High-performance thin-layer chromatography based approach for bioassay and ATR-FTIR spectroscopy for the evaluation of antioxidant compounds from Asparagus racemosus Willd. aerial parts.

Asparagus racemosus Willd. is widely used to combat various diseases owing to its medicinal properties. In this study, arial parts of A. racemosus were investigated for their total phenolic content, total flavonoid content and antioxidative potential. A high-performance thin-layer chromatography (HPTLC) method combined with effect-directed-analysis was also developed to screen the antioxidant effects of A. racemosus and quantify biologically active compounds on chromatograms from A. racemosus. Total phenolics (154 mg gallic acid equivalent/g), flavonoid contents (497 mg quercetin/g) and IC50 (15.25 μg/ml) were found to be higher in methanolic extract of A. racemosus than in n-hexane, chloroform and ethyl acetate extracts. HPTLC hyphenated with chemical derivatizations (DPPH•, p-anisaldehyde/sulfuric acid, and ferric chloride) was used to evaluate antioxidant activity and the presence of phytosterols, terpenoids and polyphenolic contents. The same compounds at 100*retention factor = 58, 68, 74 and 65 in extracts were responsible for antioxidant activity. Hyphenated HPTLC allowed a rapid characterization of the active compound with a combination of effect-directed-analysis and attenuated total reflectance-Fourier transform infrared spectroscopy. Spectral analysis of the band from attenuated total reflectance identified myricetin, quercetin, p-coumaric acid and caffeic acid as responsible for the antioxidant activity.