Isolation, Identification, and Bioactivity Evaluation of Novel Flavonoids from Alpinia Officinarum

Abstract

In this study the ethanolic extract of Alpinia officinarum was analysed for its antibacterial and antioxidant activity. The sample was extracted with 70% ethanol with Soxhlet apparatus. The bioactive compounds in the extract were identified by qualitative and quantitative phytochemical analysis. The most prevalent phytochemicals in A. officinarum were identified to be flavanoids, phenols, saponins, tannins, anthocyanin, sterols, triterpenoids, and anthraquinones. The total flavonoid conent in extract of Alpinia officinarum was analysed by Aluminium chloride colorimetric technique with Quercitin as standard. The total flavonoid content in the ethanoilc extract was determined to be 63.60mg/g. The ethanol fraction of Alpinia officinarum was subjected to thin layer chromatography. The Quercitin, Rutin, Kaempferol, Narigenin revealed a single spot with Rf value of 0.35, 0.3, 0.57, 0.25 respectively and the flavonoid fraction revealed a single spot with Rf values in the range of 0.59. The Rf value of isolated compound correlated with Kampferol. 13C NMR can be used to analyse the anomeric configurations, linkage sites, and sequence of sugars in the flavonol glycosides. Compound was identified as kaempferol 3,7,di-O-L rhamnoside with two rhamnoses. The existence of signals at 136.5 and 163.5 in the 13C NMR spectra compound corroborated the glycosylation at the C-3 and C-7 sites. The antibacterial activity of the isolated compound was analysed by agar well diffusion assay and revealed that with increase in concentration, the zone of inhibition increased and the gram negative bacteria were more susceptible. The antioxidant capability of kaempferol 3,7,di-O-L rhamnoside was analysed by DPPH assay. The percentage of inhibition increased with increase in compound concentration. The compound was confirmed to have strong antioxidant activity with IC50 concentration of 253.83µg/ml.