Antibacterial and Potential Antidiabetic Activities of Flavone C-glycosides Isolated from Beta vulgaris Subspecies cicla L. var. Flavescens (Amaranthaceae) Cultivated in Egypt

Abstract

Background: Diabetes mellitus is the most common disease in Egypt. In this context, Beta vulgaris subspecies cicla L. var. flavescens is an edible plant that has been used in traditional medicine as a therapy for treating some diseases. Objective: The current study was performed to evaluate the antibacterial and potential anti-diabetic activities of different extracts and isolated flavone C-glycoside compounds isolated from Beta vulgaris subspecies cicla L. var. flavescens leaves. Methods: Phytochemical investigation of n-butanol extract led to the isolation of five phytoconstituents. Their structures were determined by spectroscopic tools, including 1D-NMR (1H- & 13C-NMR) and 2D-NMR (HMQC & HMBC) besides the comparison of the data with the literature. The extracts and phytoconstituents were evaluated in vitro for their activity against some bacterial pathogens, which represent prominent human pathogens, particularly in hospital settings. The antibacterial activity was examined against three Gram-positive bacterial strains (Staphylococcus aureus, Staphylococcus epidermidis & Enterococcus faecalis) and five Gram-negative ones (Pseudomonas aeruginosa, Proteus vulgaris, Klebsiella pneumoniae, Proteus mirabilis & Salmonella typhimurium) relative to Ciprofloxacin as a reference drug. Furthermore, the in vitro antidiabetic activity (Type II) was evaluated using the alpha-glucosidase inhibitory assay. Results: Five flavone C-glycosides namely; Apigenin 8-C-β-D-glucopyranoside (vitexin) (1), 2''-Oxylopyranosylvitexin (2), acacetin 8-C-β-D-glucopyranoside (3), acacetin 8-C-α-L-rhamnoside (4), and 6,8-di-C-β-D-glucopyranosylapigenin (vecinin-II) (5) were isolated from n-butanol extract of B. vulgaris subspecies cicla L. var. flavescens. Compound 1 showed a promising antibacterial activity against most of the test bacterial strains with respect to the minimum inhibitory concentration values (MIC) ranged from 1.95 to 15.63 µg ml-1. On the other hand, compounds 1 and 3 demonstrated superior antidiabetic activities with IC50 values of 35.7 and 42.64 µg ml-1, respectively, while an inferior potential antidiabetic activity was recorded for compound 4 (IC50 = 145.5 µg ml-1) in comparison with Acarbose as a reference drug. Conclusion: B. vulgaris L. is an edible plant, which could be used as a natural source of antibiotic and hypoglycemic drugs.