The endophytic Fusarium strains: a treasure trove of natural products

The complexity and structural diversity of the secondary metabolites produced by endophytes make them an attractive source of natural products with novel structures that can help in treating life-changing diseases. The genus Fusarium is one of the most abundant endophytic fungal genera, comprising about 70 species characterized by extraordinary discrepancy in terms of genetics and ability to grow on a wide range of substrates, affecting not only their biology and interaction with their surrounding organisms, but also their secondary metabolism. Members of the genus Fusarium are a source of secondary metabolites with structural and chemical diversity and reported to exhibit diverse pharmacological activities. This comprehensive review focuses on the secondary metabolites isolated from different endophytic Fusarium species along with their various biological activities, reported in the period from April 1999 to April 2022.


Introduction
Currently, there is an urgent need for the discovery of new molecules to overcome the challenges that threaten human life. Health-related problems such as antimicrobial resistance, lifethreating viruses such as Covid-19, SARS, bird u, and AIDS, and cancer seriously affect people's health. 1 Scientists have been fascinated by nding secondary metabolites with novel skeletons from new natural sources. 2 One of the great sources of novel natural products for utilization in medicine and other elds is the entophytic microorganisms, which survive internally in living tissues and are ubiquitous in all medicinal plant species. 3 Endophytic microorganisms (fungi or bacteria) are capable of producing the same or similar compounds to those of the host plant without causing harm or apparent disease. 4 Endophytes provide benets in survival, biodiversity, and ecosystem abilities to enhance the response to environmental stress. 4 Endophytes might be involved in the biosynthesis of plant products; however, they might also be the producers themselves of many substances of potential use to modern medicine, agriculture and the pharmaceutical industry. 5 Fungal endophytes are a major source of anti-infective agents and other medically relevant compounds. 6 Endophytic fungi are a source of a diverse array of multidimensional bioactive secondary metabolites such as alkaloids, terpenoids, steroids, quinones, iso-coumarins, lignans, phenylpropanoids, phenols, and lactones. 7 In 2013, the Food and Drug Administration (FDA) reported that 25% of drugs were discovered from micro-organisms, among 38% natural products that were used as drugs. 8 Fusarium is considered as a member of the most dominant endophytic fungal genera in the world, characterized genetically with extraordinary discrepancy, together with its ability to grow on a wide range of substrates and their efficient mechanisms for dispersal, which affect their biology and interaction with their surrounding organisms, together with secondary metabolism that makes Fusarium an important group of fungi. [8][9][10] Fusarium genus is in the third level of endophytes aer Aspergillus and Penicillium sp. and it is a cosmopolitan genus of lamentous ascomycete fungi (Sordariomycetes, Hypocreales, Nectriaceae), which comprise more than 70 species with a wide range of hosts. [8][9][10] They are widely abundant in soil, subterranean and aerial plant parts, plant debris, and other organic substrates. 11 Fusarium is considered to be a rich source of bioactive compounds, including more than one hundred compounds with unique chemical structures, among more than three hundred compounds of various classes such as butenolides, alkaloids, terpenoids, cytochalasins, phenalenones, xanthones, sterols, and diphenyl ether and anthraquinone derivatives, with multidimensional bioactivities such as antimicrobial, antiviral, anticancer, antioxidant, antiparasitic and immunomodulating activity. 8 There are many examples of fungal endophytes that have been reported to produce bioactive metabolites similar to those originally derived from the host plant. 12 The majority of Fusarium metabolites were isolated in the period from 2017 to 2022, see Fig. 1. This review covers the literature on the isolated natural products from the fungal endophyte Fusarium species and their various bioactivities from April 1999 to April 2022.

Phylogenetic analysis
One phylogenetic tree was established according to the ribosomal 18S RNA gene sequence analysis, as shown in Fig. 2. The genus Trichoderma was used as an outgroup to gain a better overview of the diversity of Fusarium species. Even though the 18S rRNA gene is highly conserved, the Fusarium species clustered into different clades, conrming the high diversity of this genus and the diversity of chemical compounds produced by the different species of Fusarium, as mentioned in this review. Nucleotide sequences of 18S rRNA of Fusarium species and the outgroup Trichoderma were extracted from the National Center for Biotechnology Information (NCBI, https:// www.ncbi.nlm.nih.gov/). The 18S rRNA sequences were aligned using Muscle (maximum number of iterations of 10) implemented in Geneious Prime 2022.1.1 (https:// www.geneious.com). The alignment was manually curated and trimmed, and the best nucleotide model (Kimura 2-parameter + gamma distribution) was determined using MEGA X. 13 A neighbour-joining tree was computed using MEGA X with 1000 bootstrap replicates and the best model. It was shown that all of the different members of Fusarium species could be grouped together in a single cluster relative to the outgroup Trichoderma species.

F. solani
F. solani is one of the most important sources of novel and diverse pharmacologically active secondary constituents. F. solani is isolated from Taxus Brevifolia, which is considered to be an additional source of Taxol (24) that is the rst member of the taxane family to be used in cancer chemotherapy and is characterized by its limited availability, high cost and low yield from plant sources; it is used in the treatment of several different types of cancer, such as breast, ovarian, prostate, nonsmall cell lung, adeno-carcinoma, and esophagus squamous cell carcinoma. It inhibited cell proliferation of a number of cancer cell lines such as HeLa, HepG2, Jurkat, Ovcar3 and T47D with IC 50 values ranging from 0.005 to 0.2 mM for fungal taxol. 20 It induced apoptosis in JR4-Jurkat cells with a possible involvement of anti-apoptotic Bcl 2 and loss in mitochondrial membrane potential and was unaffected by inhibitors of caspase-9, -2 or -3 but was prevented in the presence of caspase-10 inhibitor. 20 However, signicant toxicities, such as myelosuppression and peripheral neuropathy, limit the effectiveness of paclitaxel-based treatment regimens. 21 F. solani was the only one strain among 153 endophytic fungi recovered from the roots, stems, and leaves of Cajanus cajan that was found to produce vitexin (5,7,4-trihydroxyavone-8-glucoside) (25), which is well known to have valuable biological properties such as anti-inammatory, anticancer, anti-nociceptive, antioxidant, anti-convulsant, cardioprotective, hypotensive, memory enhancing potential, and anti-diabetic. 22 Recently, there was a study that revealed the good osteogenic proliferation stimulating activity of vitexin that made it a lead molecule for the treatment of osteoporosis 22 The anti-neoplastic effects are due to the promotion of apoptosis and autophagy as well as the inhibition of proliferation and migration through several signalling pathways. 23 Vitexin exhibited an antihyperalgesic effect through reducing the pro-inammatory cytokine (TNF-a, IL-1b, IL-6, and IL-33) and enhancing the anti-inammatory cytokine (IL-10) production induced by carrageenan. 23 Vitexin exhibits a protective effect against cardiac ischemia/reperfusion (I/R) injury through inhibiting the I/R-induced decrease in coronary ow and ST segment elevation in EKG. 23 Vitexin signicantly reduced postprandial blood glucose both in sucrose loaded normoglycemic mice and sucrose induced diabetic rats, which demonstrates a potential role on diabetes. 23 Additionally, seven secondary metabolites were isolated from F. solani (Cassia alata Linn root), including: three naphthaquinones, anhydrofusarubin (26), fusarubin (27) and 3-deoxyfusarubin (28), one aza-anthraquinone, bostrycoidin (29), two sterols, ergosterol (30) and 3,5,9- trihydroxyergosta-7,22-diene-6-one (31), and 4-hydroxybenzaldehyde (32). 24 Interestingly, fusarubin (27) exhibited a signicant neuroprotective activity on glutamate-mediated HT22 cell death; fusarubin has been known as an inhibitor of mitochondrial NADH ubiquinone reductase, which is also known as coenzyme Q10 and is well known as a free-radicalscavenging antioxidant. 25 These studies conrm the hypothesis that endophytes can be used for the industrial production of important neuroprotective drugs. Likewise, these compounds displayed varied cytotoxic potency on vero cells, wherein 4-hydroxybenzaldehyde (32) and bostrycoidin (29) cause the death of nearly 25% of the cells, while anhydrofusarubin (26) and 3,5,9-trihydroxyergosta-7,22-diene-6one(31) killed 35% of the cells, indicating that the cell proliferation inhibition activity of these four compounds would be benecial in the anticancer treatment of kidney cancer patients. 24 In addition, fusarubin (27) exhibited highly signicant antibacterial activity against four pathogens, B. megaterium, S. aureus, P. aeruginosa and E. coli, with inhibition zones of 21-32 mm, while bostrycoidin (29) and anhydrofusarubin (26) displayed prominent potency with inhibition zones of 12-16 mm and 10-17 mm, respectively. 24 Fusarubin (27) and anhydrofusarubin (26) inhibit proliferation and increase apoptosis in cell lines derived from hematological cancers like acute myeloid leukemia (OCI-AML3) and other hematological tumor cell lines (HL-60, U937, and Jurkat); fusarubin was more potent than anhydrofusarubin, due to upregulating p 21 expression in a p 53 -dependent manner resulting in decreasing ERK phosphorylation and increasing p 38 expression, both of which increase p 21 stability. 26 The antimicrobial activity of bostricoidin and fusarubin toward Pseudomonas aeruginosa is due to stimulation of respiratory oxidation of bacterial cells and inducing cyanide-insensitive oxygen consumption. 27 Finally, bostrycoidin, anhydrofusarubin, 4hydroxybenzaldehyde and fusarubin showed signicant free radical scavenging activity with IC 50 values of 1.6 12.4, 28.9 and 34.8 mg mL −1 , respectively, compared to BHA, trolox and ascorbic acid as positive controls (IC 50 values of 1.2, 1.3 and 1.5 mg mL −1 , respectively). 24 Investigation of F. solani HDN15-410, which is a mangrove-derived fungus, isolated from the root of Rhizophora apiculata Blume, resulted in the isolation of ve fusaric acid derivatives, fusaricate H-K (33)(34)(35)(36) and fusaric acid (37), as well as two undescribed g-pyrone derivatives, fusolanone A (38)  One new naphthoquinone, 9-desmethylherbarine (51), and two aza-anthraquinone derivatives, 7-desmethylscorpinone (52) and 7-desmethyl-6-methylbostrycoidin (53), along with four known compounds, anhydrofusarubin (26), fusarubin (27), javanicin (54) and cerevesterol (55), were reported for the rst time in the Fusarium genus that was isolated from F. solani (Aponogeton undulates). In addition, compounds 52 and 53 exerted cytotoxic activity against four human tumor cell lines, i.e., HeLa cervical carcinoma, MDA MB 231 breast cancer, MIA PaCa2 pancreatic cancer, and NCI H1975 non-small-cell lung cancer, with low micromolar to submicromolar IC 50 31 Additionally, two new polyhydroxylated steroids, 2b,9adihydroxy-5a-methoxyergosta-7,22-diene (56) and 2b,6b-dihydroxy-5a-methoxyergosta-7,22-diene (57), were isolated from F. solani found in Chloranthus multistachys leaves and showed antagonistic properties against seven pathogens (Glomerella cingnlata, Alternaria brassicae, Penicillium digitatum, Botrytis cinerea, Verticillium alboatrum, Phytophthora capsici and Exserohilum turcicum) with GI $ 70%, proving their broad spectrum antimicrobial properties. 32 Camptothecin (58) and 10-hydroxycamptothecin (59) are considered to be very important precursors for the clinically potent anticancer drugs topotecan and irinotecan, and 9-methoxycamptothecin (60) was isolated from the endophytic fungal strains in Camptotheca acuminata and also from Apodytes dimidiata (Icacinaceae). 33 Camptothecin inhibits the intra-nuclear enzyme topoisomerase-I, required for DNA replication and transcription, but 10-hydroxycamptothecin has been shown to act against a broad spectrum of cancers. 34 These results strongly indicate that Fusarium spp. isolated from medicinal plants may serve as a potential source of anticancer compounds with multiple modes of action. Further investigation to isolate these active compounds in good yields followed by mode of action studies could reveal new potential drugs against multiple cancer diseases. The water-soluble salt camptothecin-sodium is highly toxic in animals, whereas its semisynthetic derivatives irinotecan and topotecan do not cause haemorrhagic cystitis because of their higher physicochemical stability and solubility at lower pH values, although this may cause myelosuppression, neutropenia and, to a lesser extent, thrombocytopenia, which are dose-limiting toxic effects of topotecan. 35 The chemical investigation of F. solani JS-0169 found in Morus alba leaves resulted in six compounds, including: one new g-pyrone, 6-((9R,11R,E)-13-hydroxy-9,11-dimethyloct-7-en-7-yl)-2-methoxy-4H-pyran-4-one (61), a known g-pyrone, fusarester D (62), and two known naphthoquinones, karuquinone B (63) and solaniol (49). 25 3,6,9-trihydroxy-7-methoxy-4,4-dimethyl-3,4-dihydro-1Hbenzo[g]isochromene-5,10-dione (64), 3-O-methylfusarubin (65) and fusarubin (27) were isolated from F. solani present in Glycyrrhiza glabra (Liquorice). These compounds were found to exert antimicrobial activity against various bacterial strains, such as E. coli, S. pyogenes, Klebsiella, B. cereus, and S. aureus (MIC: <1 to 256 mg mL −1 ), besides their inhibition against Mycobacterium tuberculosis strain H37Rv (MIC: 8-256 mg mL −1 ). 36 Further investigation of these compounds could lead to new antibiotics with multi-target activity; this feature is needed to prevent the future development of pathogen

F. lateritium
Three tricyclic pyridone alkaloids, identied as 6-deoxyoysporidinone (96), 4,6 ′ anhydrooxysporidinone (97) and sambutoxin (98), were separated from F. lateritium associated with Cornus officinalis fruits. 46 4,6 ′ -Anhydrooxysporidinone was shown to protect HT22 cells through several mechanisms such as the inhibition of glutamate-induced cytotoxicity, accumulation of intracellular reactive oxygen species, increasing superoxide anion (Ca 2+ ) production, and depolarization of the potential of the mitochondrial membrane. 46 Additionally, its ability to inhibit cytochrome c release and cleave caspase-9 and -3 in glutamatetreated HT22 cells led to inhibition of apoptotic cell death. 46 Two new cyclic lipopeptides, acuminatums E (99) and F (100), with four known cyclic lipopeptides, acuminatums A-D (101-104), were obtained from Adenanthera pavonina leaves, and these compounds exhibited antifungal activity against Penicillium digitatum with inhibition zones ranging from 1.5 mm to 9.0 mm in which acuminatum F (100) was the strongest with an inhibitory zone range of 6.5-9.0 mm. 47 These investigations showed that Fusarium spp. can also produce compounds that can serve as a good starting point for the discovery of new antifungal drugs. Therefore, further investigations are needed for the discovery of new antifungal drugs. The number of compounds isolated from this species is very limited and they are shown with those of F. subglutinans in Fig. 11.

F. subglutinans
F. subglutinans harbored in Tripterygium wilfordii vine is a good source of natural promising new immunosuppressive drugs that can inuence the immune system of animals, such as subglutinols A (105) and B (106), which are diterpene pyrones isolated from Fusarium subglutinans that are of interest in the identication of compounds useful in the treatment of patients undergoing organ transplantation to avoid rejection. 48 Subglutinol A was effective in abolishing inammatory cytokine production by skewed Th1 or Th17 CD4 + T cells, which is a hallmark of autoimmune disease. 49 Subglutinols A and B are equipotent in the mixed lymphocyte reaction (MLR) assay and thymocyte proliferation (TP) assay (IC 50 = 0.1 mm). 50 Subglutinol A is an immunosuppressive drug without undesirable side effects to bone structure. 50

F. redolens
The fungal strain 6WBY3 isolated from Fritillaria unibracteata var. wabuensis (fresh bulbus) yields two steroidal alkaloids, peimisine (107) and imperialine-3b-D-glucoside (108). 51 Peimisine helps in getting rid of sputum and cough symptoms, it is considered to be a good lead for new anti-tumor drugs, and it exhibits potent inhibitory effects on angiotensin converting enzyme, due to its improvement in caspase-3 expression level, together with the signicant inhibition of tumor angiogenesis and apoptosis induction. 51 F. redolens fermentation broth was able to produce taxol (24) from Himalayan Yew bark, whose presence in the fungal broth was determined by reverse-phase HPLC and mass spectroscopy, and it is considered to be a new source for the production of this important anticancer drug. 52 The crude extract of F. redolens isolated from Olive (Olea europaea L.) stem resulted in the isolation of chrysophanol (109) and fumaric acid (110); chrysophanol is an anthraquinone having several pharmacological activities such as anticancer, hepatoprotective, neuroprotective, anti-inammatory, and antiulcer, in addition to its antimicrobial potency against various microbial strains, including: C. albicans, C. neoformans, T. mentagrophytes, and A. fumigatus, with MIC values of 50, 50, 25, and 50 mg mL −1 . 53 Fumaric acid (110) is one of the more commonly produced secondary metabolites and it is used in the treatment of psoriasis or multiple sclerosis. Clinical studies in psoriasis showed a reduction of peripheral CD4 + and CD8 + Tlymphocytes due to the ability of fumaric acid esters to induce apoptosis. 53 Fumaric acid esters may cause both renal Fanconi syndrome and acute kidney injury. This effect may be ameliorated by antagonism of the organic anion transporter with probenecid. 54 Beauvericin (BEA) (72) was also obtained from this fungal endophyte isolated from rhizomes of the Chinese medicinal plant Dioscorea zingiberensis. 55 Beauvericin causes cytotoxicity in several cell lines and has the ability to produce oxidative stress at the molecular level; its mechanism of action seems to be related to its ionophoric activity, which increases ion permeability in biological membranes. 56 Moreover, BEA is genotoxic (causing DNA fragmentation, chromosomal aberrations and micronucleus) and causes apoptosis with the involvement of the mitochondrial pathway. 56 Despite its strong cytotoxicity, no risk assessment has been carried out by authorities due to a lack of toxicity data. 56 Beauvericin has the potential to be an antibacterial drug, with IC 50 values between 18.4 and 70.7 mg mL −1 against six tested bacterial strains (B. subtilis, S. haemolyticus, P. lachrymans, A. tumefaciens, E. coli and X. vesicatoria). 55 The chemical structures of F. redolens are shown in Fig. 11.   58 The crude extract of a pure F. incarnatum culture residing in the embryo of viviparous propagule was analyzed by HPLC-MS, resulting in the observation of various highly lipophilic compounds such as coriolic acid (121), didehydrocoriolic acid (122) and cis-12,13epoxy-11-hydroxyoctadec-9-enoic acid (123). 59 Coriolic acid is a natural compound that inhibits the formation of mammospheres and induces BCSC apoptosis; it also decreases the subpopulation of CD high 44 /CD low 24 cells, a cancer stem cell (CSC) phenotype, and specic genes related to CSCs, such as Nanog, Oct 4 , and CD 44 . 60 Coriolic acid could be a novel compound to target breast cancer stem cells via regulation of c-Myc. 60 The chemical structures of F. incarnatum are shown in Fig. 12.

F. sambucinum
Bioactivity-based phytochemical investigation of F. sambucinum TE-6L harbored in Nicotiana tabacum L. led to the discovery and separation of two new angularly prenylated indole alkaloids with pyrano[2,3-g] indole moieties, amoenamide C (124) and sclerotiamide B (125), and four known biosynthetic congeners, sclerotiamide (126), notoamide B (127), speramide A (128), and notoamide D (129). 61 All these compounds displayed selective antibacterial activity with MIC values ranging from 1.0 to 32 mg mL −1 . 61 Amoenamide C (124) demonstrated potent activity against P. aeruginosa with a MIC value of 1 mg mL −1 , which was better than that of the positive control chloromycetin (MIC = 4 mg mL −1 ). 61 Furthermore, sclerotiamide showed stronger T-2 toxin (130), neosolaniol (131) and HT-2 toxin (132) together with two new trichothecenes, 4b-8a-diacetoxy-12,13-epoxytrichothec-9-ene-3a,15-diol (133) and 4b-acetoxy-12,13-epoxytrichothec-9-ene-3a,8a,15-triol (134), were isolated from the bean bull culture ltrate of the F. sporotrichiides M-1-1 strain. 62 These compounds showed no antimicrobial activity, but this wasn't enough to classify them as inactive, therefore there is a need for further study of these compounds in comparison to others to reveal their outstanding potency. 62 T-2 toxin is one of the most common toxic trichothecene mycotoxins due to its potent neurotoxicity. 63 T-2 toxin can cross the blood-brain barrier due to its lipophilic nature and accumulate in the central nervous system (CNS) to cause neurotoxicity. 63 The underlying mechanism is that T-2 toxin undergoes metabolism to produce epoxides that are extremely toxic compounds reacting with nucleophiles and promoting ROS production that mediate oxidative stress and mitochondrial dysfunction. 63 These effects are compounded by the ability of T-2 toxin to deplete GSH in neuronal cells and brain tissues. 63 Furthermore, exposure to T-2 toxin during pregnancy results in embryotoxicity and the abnormal development of offspring. 64 The chemical structures of the isolated compounds of F. sambucinum and F. sporotrichioides are shown in Fig. 13.

F. tricinctum
F. tricinctum (Corda) Sacc. is a food contaminating mold that produces toxic metabolites with a wide distribution in crops and plant products. 65 Two novel nor-sesquiterpenoids (135 and 136) containing a new tetrahydrofuran skeleton were separated from F. tricinctum harbored in the root of Ligusticum chuanxiong, and these compounds were elucidated as (R,2E,4E)-6-((2S,5R)-5ethyltetrahydrofuran-2-yl)-6-hydroxy-4-methylhexa-2,4-dienoic acid (135) and (S,2E,4E)-6-((2S,5R)-5-ethyltetrahydrofuran-2-yl)-6-hydroxy4-methylhexa-2,4-dienoic acid (136). The cytotoxic potency of these compounds was evaluated by using MTT assay against HCT116, MCF-7, A549 and MV4-11 cancer cell lines, wherein compound (136) exhibited moderate growth inhibition against the MV4-11 cell line with an IC 50 of 22.29 mM. 66 The co-  69 Two new rare irregular sesquiterpenes, tricinonoic acid (156) and tricindiol (157), and two known furanopyrrolidones, NG-391 (47) and NG-393 (48), were isolated from the EtOAc extract of F. tricinctum, found in Rumex hymenosepalus root. 65 Using the One Strain Many Compounds (OSMAC) approach on F. tricinctum resulted in an up to 80-fold increase in the accumulation of new natural compounds such as fusarielin J (158), fusarielin K (159) and fusarielin L (160) together with the known derivatives fusarielins A (161) and B (162). 70 Although fusarielin J (158) exhibited cytotoxic activity against the human ovarian cancer cell line (A2780), with an IC 50 value of 12.5 mM, the other fusarielins showed very weak activity (436 mM) in the same assay. 70 Additionally, enniatins, which are a group of antibiotics with six-membered cyclic depsipeptides, formed by the union of three molecules of D-a-hydroxyisovaleric acid and three Nmethyl-L-amino acids, were identied from the F. tricinctum Corda endophyte in the fruits of Hordeum sativum Jess and Aristolochia paucinervis, and they were named enniatins A (163), A1 (164), B (165), B1 (166), B2 (167) and Q (168). 71 Among these, enniatin Q is a new analog of ENA and the occurrence of EN B2 was reported for the rst time from this endophyte. 71 Enniatins exhibited antimicrobial and cytotoxicity activities against human cells; they also had a limited hemolytic effect, yet were found to be toxic at low doses to nucleated human cells causing apoptosis, mitochondrial damage, and reactive oxygen species production. They also interact with bacterial lipids, causing low to no membrane permeabilization, but induced membrane depolarization and inhibition of macromolecule synthesis. 72 Enniatins have hypolipidemic effects related to their ability to inhibit acyl coenzyme A cholesterol acyltransferase (ACAT) and triglyceride biosynthesis. 72 The methanol extract of enniatins showed mild antileishmanial activity against L. donovani ATTC 39930D with the IC 50 value of 16.96 mg mL −1 and the IC 90 value of 30.4 mg mL −1 . 71 It also displayed moderate cytotoxic activity against HepG2 and C6 cells (IC 50 values of 10-25 mM), and high toxicity against H4IIE cells (IC 50 values of 1-2.5 mM). 71 The hydro-distillation of F. tricinctum found in Paris polyphylla var yunnanensis resulted in a volatile oil, which when analyzed by gas chromatography-mass spectrometry (GC-MS) consisted of trans-1,2,3,3a,4,7a-hexahydro-7a-methyl-5H-inden-5-one (169), 2-methylene-4,8,8-trimethyl-4-vinyl bicyclo [5.2.0] nonane (170), and 2,6-dimethyl-6-(4-methyl-3-pentenyl) bicyclo [3.1.1] hept-2-ene (171). 73 The volatile oil exhibited antimicrobial activity against eight bacterial strains, A. tumefaciens, E. coli, P. lachrymans, S. typhimurium, X. vesicatoria, B. subtilis, S. aureus and S. haemolyticus, with varied MIC values ranging from 25 to 45 mg mL −1 and 100 to 225 mg mL −1 against C. albicans and M. oryzae, respectively. 73 Shikonin (172) is a naphthoquinone that was found to be produced only by F. tricinctum harbored in Lithospermum officinale L. roots. (family: Boraginaceae). 74 Shikonin exhibited potent antibacterial activity against Grampositive bacteria such as B. subtilis, E. faecium, and S. aureus at MIC values ranging from 0.30 to 6.25 mg mL −1 . 74 In contrast, it showed no activity against Gram-negative strains such as M. luteus, E. coli, and P. aeruginosa; shikonin exhibited potent anti-HCV activity, with an effective concentration (EC 50 ) of 25 ng mL −1 , which was far lower than that of the positive control ribavirin (EC 50 = 2.6 mg mL −1 ). 74 Another study on shikonin and its derivatives revealed its strong cytotoxic potency in various cancer cell lines (cervical cancer cell line HeLa, colon cancer cell line Hct116, hepatocellular carcinoma cell line Hep3B, and a lung cancer cell line (A549)) having a 50% growth inhibition range of 0.5-3.0 mM. 74 Shikonin is known to suppress proliferation and induce apoptosis in a variety of cancer cell lines by inhibiting cell cycle progression, disrupting Ca 2+ homeostasis, inducing oxidative stress and triggering mitochondrial dysfunction. It also activates caspases-3, -8 and -9, and K + efflux, and regulates Bax, Bcl-2, p 53 and caspase-3 expression. 75 Likewise, new sesquiterpenoid ethers with unique skeletons obtained from F. tricinctum of Salicornia bigelovii were named fusartricin (173) and fusarielin B (162) and displayed noticeable antimicrobial potency against E. aerogenes, M. tetragenu and C. albicans with MIC values of 19, 19 and 19 mM, respectively. 76 Furthermore, the study of one kiwi endophytic fungus, F. tricinctum, led to the separation of nine new imidazole alkaloids,  77 It is clear from these investigations that Fusarium species are the source of not only broad-spectrum antimicrobial compounds but also compounds with specic activity against a target pathogen. The chemical structures of F. tricinctum are shown in Fig. 14-16.

F. equiseti
F. equiseti is a good source of various classes of secondary metabolites, as well as a pair of undescribed 3-decalinoyltetramic acid (3DTA) E/Z diastereomers, decalintetracids A (190) and B (191). 78 Both of them are considered to be potential natural herbicides, owing to their phytotoxic potency toward A. retroexus L. and A. hybrid. 78 Additionally, a new glucitol, diglucotol (192), together with ve known compounds, cerebroside C (193), Nb-acetyltryptamine (3), 3b,5a,9a-trihydroxy-(22E,24R)-ergosta-7,22-dien-6-one (31) 79 Cerevisterol is a natural agent for treating inammatory disease. It suppresses the LPSinduced production of NO and PGE 2 , likely by reducing the expression of iNOS and COX-2. CRVS also decreases the expression of pro-inammatory cytokines, such as TNF-a, IL-6, and IL-1b. CRVS halted the nuclear translocation of NF-kB by blocking the phosphorylation of inhibitory protein kBa (IkBa) and suppressing NF-kB transactivation. It also suppresses the mitogen-activated protein kinase (MAPK) signaling pathways. CRVS treatment also inhibited the transactivation of AP-1 and the phosphorylation of c-Fos. 80 Their chemical structures are shown in Fig. 17.
The fungal endophyte Fusarium sp. isolated from Monardacitriodora Cerv. ex leaves showed a good ability to produce plant-like volatile organic compounds that are industrially important, in particular hexanal (221), (5E)-5-ethyl-2-methyl-5hepten-3-one (222) and acoradiene (223) representing around 84.57% of the total VOCs. 90 Additionally, Fusarium sp. isolated from Mentha longifolia L. (Labiatae) roots grown in Saudi Arabia produced cyclo depsipeptide fusaripeptide A (224), together with three known compounds, adenosine (225), 2[(2hydroxypropionyl)amino]benzamide (226), and cyclopentanol (227). 91 Notably, fusaripeptide A showed potent antifungal activity against C. albicans, C. glabrata, C. krusei, and A. fumigates with IC 50 values of 0.11, 0.24, 0.19, and 0.14 mM, respectively. Fusaripeptide A serves as a good starting point for the discovery of new antifungal drugs. In addition, it showed signicant anti-malarial activity toward P. falciparum (D6 clone) with an IC50 value of 0.34 mM. 91 However, it showed potent cytotoxic activity toward L5178Y and moderate activity against PC 12 with IC 50 values of 5.71 and 9.55 mM, respectively, in comparison to doxorubicin (IC 50 values of 4.60 and 5.71 mM, respectively). 91 Likewise, Fusarium in (a new iso-coumarin derivative) (228) together with two known related resorcylic acid lactones, aigialomycin D (229) and pochonin N (230), was obtained from Fusarium sp. LN-10, originating from the leaves of Melia azedarach, and these compounds displayed signicant toxicity toward brine shrimp larvae at a concentration of 10 mg mL −1 with mortality rates (%) of 78.2, 76.7 and 82.8, respectively, using chaetomugilin A as a positive control, which showed a mortality rate of 78.3% at the same concentration. 92 The chemical investigation of the crude extract of  93 Three helvolic acid derivatives named helvolic acid methyl ester, which is a new compound (237), helvolic acid (238), and hydrohelvolic acid (239) were isolated from Fusarium sp. in Ficus carica leaves and exhibited potent antifungal and antibacterial activities. 94 Helvolic acid (238) showed potent cytotoxicity against different human cancer cells upon the coadministration of 10 mg per kg per day helvolic acid with 20 mg per kg per day cyclophosphamide (CTX)-a well-known chemotherapy drug-resulting in promising antitumor activity with a growth inhibitory rate of 70.90%, which was much higher than that of CTX alone (19.5%), and its mechanism of action may related to the Wnt/b-catenin signaling pathway. 95   antifungal activity against Cladosporium cladosporiodes with inhibition zones of 12.0 and 9.5 mm, respectively, using nystatin as a positive control, which exhibited a halo diameter of 26 mm. They also exhibited weak cytotoxic activity toward human ovarian carcinoma sensitive (A2780 sens) with growth inhibition values of 48% and 42%, respectively. 100 The chemical structures of 241-274 are shown in Fig. 21 102 Consequently, two sterols, 5a,8a-epidioxyergosta-6,22-dien-3b-ol (278) and ergosta-8(9)22-dien-3b,5a,6b, 7-alpha-tetraol (279), and one fatty acid, butanedioic acid (280), were obtained from Fusarium sp. Ppf4 isolated from Paris polyphylla var. yunnanensis Hand.-Mazz rhizomes. 103 Compound 278 was the most potent antimicrobial compound toward X. veisicatoria and M. oryzae with IC 50 values of 86.7 and 92.8 mg mL −1 , respectively. 103 Ginsenoside (281) isolated from the Fusarium sp. PN8 endophyte of Panax notoginseng exhibited antibacterial activity (MIC 1.6-3.2 mg mL −1 ) against E. coli, P. aeruginosa, B. subtilis, S. aureus ATCC25923, and S. lutea, and two yeast strains (C. albicans and S. cerevisiae). 62 It also showed anti-inammatory action due to induction of the polarization of M1 and M2 macrophages and microglia and the contribution of M2-polarized cells to the suppression of inammation progression and promotion of inammation resolution. 104 Fusarielin E (282), which is a new antifungal drug, was isolated from the culture broth of F. sp. CR377 separated from Selaginella pallescens, and it revealed signicant biological activity against Pyricularia oryzae (MIC of  compared to the antitumor agent mitomycin C, which exhibits an IC 50 of 5.3 mg mL −1 toward these same two cell lines. 106 Sansalvamide is a potentially promising anti-MCV agent as it is active against the virus-encoded type-1 topoisomerase, an enzyme likely to be required for MCV replication. 107 Sansalvamide A was found to inhibit topoisomerase-catalyzed DNA relaxation; it also inhibited DNA binding and therefore covalent complex formation, but not resealing of a DNA nick in a preformed covalent complex, thereby specifying the part of the protein sensitive to sansalvamide A. 107 108 Eleven new dihydronaphthalenones (296-306), together with ve known compounds, were isolated from the endophytic fungus Fusarium sp. BCC14842, 4hydroxydihydronorjavanicin (296), dihydronaphthalenone (297), and its diastereomer (298), 5-hydroxydihydrofusarubins A, B and D (299-301), and the methyl ether derivatives known as 5-hydroxy3-methoxydihydrofusarubin A (302), 5-methoxydihydrofusarubin B (303), 3,5-dimethoxydihydrofusarubin B (304), 5hydroxy-3-methoxydihydrofusarubin D (305), 3,5-dimethoxydihydrofusarubin D (306), and 5-hydroxydihydrofusarubin C (307), javanicin (54), bostrycoidin (29), anhydrofusarubin (26), and 3-Omethylfusarubin (65). 109 Compounds 298 and 302 exhibited weak to moderate anti-mycobacterial activity against Mycobacterium tuberculosis ranging from 25.0-50.0 mg mL −1 , while compounds 297, 299, 327, 300, and 307 showed only cytotoxic activity against KB and NCI-H187 cell lines (IC 50 values of 1.62-31.69 mg mL −1 ). 109 Fusarium species are capable of producing quinine (308) and cinchonidine (309) in synthetic liquid medium from different plant organs of Cinchona calisaya. 110 Quinine has been used as the main medication for malaria disease due to its effectivity against the erythrocytic stage of the parasite P. falciparum. 110 Cinchonidine has antimalarial activity, but it is not as effective as quinine. 111 Quinine's antimalarial activity is due to its ability to inhibit the formation of hemozoin by forming ve coordinate complexes with the porphyrin through their benzylic C-9 hydroxy groups, as well as an intramolecular hydrogen bond between the propionate side chain of Fe(III) PPIX and the protonated quinuclidine nitrogen atom of the alkaloid. This complex inhibits the formation of hemozoin. 111 This could justify further chemical investigation of these species for novel antimalarial drug discovery. The chemical structures 275-309 are shown in Fig. 23 and 24.
The above data demonstrate the outstanding biocontrol potential of members of the genus Fusarium and supports the continued investigation of these fungi as sources of potential biocontrol agents. This genus is a prolic source of bioactive secondary metabolites and can contribute in a spectacular way to improving human health. We have reviewed the ability of endophytic Fusarium species to produce many useful metabolites applicable in the pharmaceutical and agricultural industries, and explained the mechanism of action of some compounds. Most of the isolated metabolites from endophytic Fusarium species would make promising lead compounds for the development of anti-inammatory, antibacterial, antifungal, antiviral, and cytotoxic agents (Table 1).

Conclusion and future perspectives
Fungal endophytes are the fungal population of the internal tissues of plants causing no apparent symptoms of disease. These endophytes are able to produce certain phytoconstituents originally attributed to their host plant, which is thought to be due to genetic recombination between the endophyte and the host plant that occurred in the evolutionary period. In addition, fungal endophytes are reported to produce new secondary metabolites, which may be totally different from those of the host plant, so they are a precious source of novel bioactive natural products and an alternative source for phytochemicals initially produced by higher plants. The Fusarium genus is among the well-known genera of fungal endophytes Fusarium sp. C. calisaya Anti-malarial with many different species. Fusarium endophytes are considered to be a rich source of new secondary metabolites with valuable biological activities and a promising basis for drug discovery. Metagenomics studies revealed the potential for the discovery of new species within the genus Fusarium as there are several species that remain unidentied. This review reported the various phytoconstituents isolated from fourteen Fusarium species; F. chlamydosporum, F. proliferatum, F. solani and F. oxysporum are among the most isolated and identied endophytic Fusarium strains, see Fig. 25. The literature survey revealed that the varied abundance of secondary metabolites differs from year to year, for example only 15 compounds were reported from 1999 to 2010, while from 2011 to 2016, there was a signicant increase in newly identied compounds, up to 112. The recent advances in chemical tools such as LC-MS could explain the increased discovery of new metabolites. Fusarium species have the ability to produce a varied array of secondary metabolites such as sterols, polyketides, alkaloids, terpenes, peptides and other compounds, see Fig. 26. Alkaloids are the most prolic chemical class produced by different Fusarium species followed by peptides and naphthoquinones, as illustrated in Fig. 26. Most of the isolated secondary metabolites showed diverse biological activities, which ensures that the curiosity in studying Fusarium endophytes is increased. Three hundred and nine compounds were reported, among them ninety two novel compounds, representing 23% of the isolated compounds, see Fig. 28. The isolated compounds exhibited multidimensional bioactivities, such as antimicrobial, antiviral, anticancer, antioxidative, anti-parasitic and immunomodulatory, see Fig. 27. Further investigations are recommended concerning endophytes to achieve promising scientic discoveries; these investigations should be directed toward fungal endophytes associated with plants of high medicinal value in order to produce the same phytochemicals as those isolated from the plants in an economical way. In addition, fungal endophytes can be manipulated genetically in order to produce high concentrations of certain natural products with high medicinal importance. Finally, intensive attention should be paid to the study of the mechanism of action of the frequently isolated fungal metabolites, such as alkaloids, peptides and naphthoquinones.

Conflicts of interest
There are no conicts to declare.