Structure Elucidation and Antioxidant Activity of the Phenolic Compounds from Rhynchosia suaveolens

Abstract

A new benzophenone, 2-hydroxy-3,4-dimethoxybenzophenone (1), together with a known C-glycosylxanthone, mangiferin (2) and two known C-glycosylflavones, isovitexin (3) and isoorientin (4), were isolated from the flowers of Rhynchosia suaveolens DC. (Fabaceae). The structure of the new compound (1) and the known compounds (2-4) were elucidated by extensive 1D and 2D NMR spectral studies. The plant extracts, as well as the isolated compounds, were evaluated for their total phenolic content (TPC), total flavonoid content (TFC) and DPPH radical scavenging activity. Among the isolated compounds, mangiferin (2) and isoorientin (4) showed significant radical scavenging activity comparable with that of ascorbic acid.

Phytochemistry and pharmacological activities of the genus Rhynchosia: a comprehensive review

“…For example, Rhynchosia scarabaeiods L. (known as 'gadi chikkudu kaya') has been used to treat various bacterial diseases like dysentery, diarrhea and skin infections (Challa et al 2011). Another endemic species of South India, Rhynchosia suaveolens DC is reported as antioxidant and antibacterial agent (Khan and Shoeb 1984;Rammohan et al 2015). The whole plant of Rhynchosia pseudo-cajan Cambess is widely distributed in Pakistan and is used to treat oxidative stress through antioxidant principles (Riaz et al 2011).…”

“…Besides the above revealed flavonoids, two xanthone-C-glycosides (Fig. 7), mangiferin (58) and isomangiferin (59) (Adinarayana and Chetty 1985;Rammohan et al 2015) have been isolated from R. suaveolens. It is expected that the co-occurrence C-glycosylflavonoids and C-glycosylxanthones in the same source R. suaveolens is due to chemotaxonomic prominence.…”

“…Moreover, two polyhydric alcohols such as d-pinitol and d-inositol were also isolated from the leaves of R. beddomei (Adinarayana et al 1979 andAdinarayana et al 1980c). A unique trioxygenated simple benzophenone (70) was reported as a new chemical constituent from the flowers of R. suaveolens (Rammohan et al 2015).…”

“…Therefore, many researchers have focused on natural antioxidants because they serve as primary ingredients to balance the oxidative damage against free radicals. Flavonoids are the hugest group of secondary metabolite occuring in plants which show 14, mangiferin (58) and 2-hydroxy-3,4-dimethoxybenzophenone (70), which were tested for 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (Rammohan et al 2015). Among them, compounds 58 and 14 showed prominent antioxidant activity with IC 50 51.7 and 57.7 µg/mL, respectively, comparably with positive control ascorbic acid (IC 50 34.2 µg/mL).…”

Phytochemical Screening, Antimicrobial, and Antioxidant Activities of Root and Leaf Extracts of Leucas Aspera

“…In vitro, antioxidant activity of the root and leaf extracts was evaluated by DPPH free radical scavenging assay [25]. 1 ml of each extract at selected concentrations (25,50,75, and 100 μg/ml) was mixed with 2 ml of DPPH solution. The reaction mixture was incubated for 30 min at room temperature, and absorbance was recorded at 517 nm.…”