Flavonoidal constituents, antioxidant, antimicrobial, and cytotoxic activities of Dipterygium glaucum grown in Kingdom of Saudi Arabia

Background: Dipterygium glaucum Decne. herb is one of the common traditional plants with multiple medicinal uses. Objective: To isolate the major constituents and to investigate the antioxidant, antimicrobial, and cytotoxic activities of this herb. Materials and Methods: Methanolic extract of D. glaucum herb was fractionated using n-hexane, dichloromethane, and n-butanol. Butanol fraction was chromatographed using column chromatography and preparative thin layer chromatography to isolate the major constituents. Isolated compounds were elucidated by means of spectroscopic methods, including 1D, 2D NMR (¹H, ¹³C, DEPT, COSY, HSQC, HMBC, NEOSY) and MS analysis. Total phenolic content using Folin–Ciocalteu reagent and antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay of the total methanolic extract were evaluated. Cytotoxic potential of both methanolic extract and butanol fraction was tested using a crystal violet viability assay. Antimicrobial activities of both extracts were investigated using diffusion agar technique. Results: Apigenin 6, 8-di-C-glucopyranoside (vicenin-2), quercetin-3'-O-methyl-3-O-glucopyranoside, quercetin-3'-O-methyl-3-O-galactopyranoside, quercetin-3-O-β-D-glucopyranoside, and quercetin-3-O-β-D-galactopyranoside were isolated and elucidated. Total phenolic content was (83.89 mg gallic acid equivalent/g extract). The EC₅₀value of scavenging DPPH radical was 152.0 ± 2 μ g/mL. Butanol fraction showed the highest cytotoxic activity against cervical and breast carcinoma cells (IC₅₀ 3.6 and 6.1 μ g/mL, respectively). Both methanolic extract and butanol fraction showed wide spectrum antimicrobial activity against Gram-positive and Gram-negative bacteria and some fungi. The highest activity was from methanolic extract against Enterococcus faecalis (83.25%) and against Candida tropicalis (77.03%) as compared to reference antibiotics. Conclusion: Data obtained from this study demonstrate that D. glaucum possesses significant antioxidant, cytotoxic, and antimicrobial activities which could be ascribed to its flavonoidal content.