Lotusin A: a novel pyrrole terpenoid hydrid from lotus roots (Nelumbo nucifera Gaertn.)

Abstract

Nelumbo nucifera Gaertn. has been used as a traditional medicine and food. To date, many unknown constituents have been discovered. Most of the researches on secondary metabolites and their pharmacological properties focus on alkaloid derivatives. In this study, a novel pyrrole terpenoid hydrid, lotusin A (1), and five reported substances, cholestanol (2), stigmast-4-en-3-one (3), quercetin (4), isorhamnetin (5), and norartocarpetin (6), were isolated from the methanol extract of the roots of N. nucifera Gaertn. The structures (1–6) were identified via spectroscopic analyses of NMR (1D and 2D), HR-ESIMS, and comparisons with those previously reported in the literature. Compound 1, a pyrrole terpenoid hydrid, is a unique isolate from plant natural products. Compounds 1 and 2 exhibited inhibitory activity against NO production, while all compounds showed growth inhibition of six bacterial strains. Results indicated that 1 moderately inhibited NO production with an IC₅₀ value of 21.5 µM, but no inhibition of microbial growth was observed at a concentration of 10 µM. Besides, compound 1 exhibited good inhibition of α-glucosidase (IC₅₀ = 18.2 µM); in contrast, this result was not observed for other compounds. From the result of molecular docking data, 1 has good interaction to with both of pro-inflammatory cytokines (iNOS, COX-2, TNF-α, IL-1β, and IL-6); transcription factors (Nrf2 and NF-κB), diabetes enzyme with binding energies of −6.4, −6.4, −5.0, −5.8, −6.1 kcal mol⁻¹; −6.1, −6.6 kcal mol; and −6.4 kcal mol⁻¹, respectively, resulted that 1 is the promising candidate for anti-inflammatory and α-glucosidase inhibition. Moreover, in silico ADMET and toxicity predictions indicated that 1 had favourable safety and pharmacokinetic profiles.