RESUMO
Begonia nelumbiifolia is a traditional edible plant consumed and commercialized in the northern highlands of Puebla, México. The present study reports the seasonal variation in proximate analysis as well as organic acids, carotenoids and flavonoids content in both leaves and stalks of this plant. The stalks contained low concentrations of protein (~3%), fiber (~1.5%) and nitrogen free extract (~0.26%) during the time of study. Both organs showed contents of oxalic acid (91-103 mg 100 g-1 FW), ascorbic acid (50-65 mg 100 g-1 FW), lutein (1-2.5 mg 100 g-1 FW), ß-carotene (1-3 mg 100 g-1 FW), quercetin (1.3-2.7 mg 100 g-1 DW) and rutin (0.5-1.7 mg 100 g-1 DW). Antioxidant activity against DPPH was observed by the stalk extracts from 30% methanol (IC50, 0.21-0.37 mg L-1), pure methanol (IC50, 0.14-0.21 mg L-1) and hexane: acetone (IC50, 0.77-1.21 mg L-1). In vitro anti-HMG-CoA reductase (IC50, 0.07-0.36 mg L-1) and anti-alpha-glucosidase (IC50, 0.28-0.43 mg L-1) activities were observed in extracts from the edible stalks from pure methanol and 30% methanol. The leaf extracts from 30% methanol inhibited the growth of Pseudomonas syringae pv. tabaci TBR2004 (MIC, 254 µg mL-1), P. syringae pv. tomato DC3000 (MIC, 423 µg mL-1), P. syringae pv. glycinea (MIC, 605 µg mL-1) and Clavibacter michiganensis AB299158 (MIC, 162 µg mL-1). B. nelumbiifolia contained valuable phytochemicals associated to nutraceutical and biological properties. However, the consumption of the fresh stalks must be carefully considered because of the high oxalate content.
RESUMO
This study presents a phytochemical investigation of Lepionurus sylvestris leaf extracts and their anti-diabetic activities. Traditionally, L. sylvestris leaves were used as vegetables and food in local recipes, but the root extracts of the plant can also be used in body tonic and erectile dysfunction treatments. Following a preliminary anti-diabetic activity screening test, the 80% ethanolic leaf extract exhibited potent anti-alpha glucosidase activity. So, the leaves' active components were selected for further investigation. Firstly, the plant was extracted via maceration using lower to higher polarity solvents such as hexane, ethyl acetate, ethanol, and water, respectively, to obtain the four crude extracts. Then, the phytochemicals contained in this plant were investigated via classical column chromatography and spectroscopy techniques. Anti-diabetic activity was evaluated via anti-alpha glucosidase and insulin secretagogue assays. The results showed that five compounds were isolated from the fractionated ethanolic leaf extract: interruptin A; interruptin C; ergosterol; diglycerol; and 15-16-epoxy-neo-cleoda-3,7(20),13(16),14-tetraene-12,17:18,19-diolide, a new diterpene derivative which is herein referred to as lepionurodiolide. Interruptin A and the new diterpene derivative exhibited the greatest effect on anti-alpha glucosidase activity, showing IC50 values of 293.05 and 203.71 µg/mL, respectively. Then, molecular docking was used to study the sites of action of these compounds. The results showed that interruptin A and the new compound interacted through H-bonds with the GLN279 residue, with a binding energy of -9.8 kcal/mol, whereas interruptin A and C interacted with HIS280 and ARG315 a with binding energy of -10.2 kcal/mol. Moreover, the extracts were investigated for their toxicity toward human cancer cells, and a zebrafish embryonic toxicity model was used to determine herbal drug safety. The results indicated that ethyl acetate and hexane extracts showed cytotoxicity to both Hela cells and human breast adenocarcinomas (MCF-7), which was related to the results derived from using the zebrafish embryonic toxicity model. The hexane and ethyl acetate presented LC50 values of 33.25 and 36.55 µg/mL, respectively, whereas the ethanol and water extracts did not show embryonic toxicity. This study is the first of its kind to report on the chemical constituents and anti-diabetic activity of L. sylvestris, the leaf extract of which has been traditionally used in southern Thailand as a herbal medicine and food ingredient.