The antioxidant index and chemometric analysis of tannin, flavonoid, and total phenolic extracted from medicinal plant foods with the solvents of different polarities
Ng, Z; Samsuri, SN; Yong, P
This study aimed to evaluate the effect of four solvents (water, methanol, ethyl acetate, and n-hexane) on the extraction of total phenolic content (TPC), tannin, flavonoid, ferric reducing power (FRAP), and radical scavenging activity from Centella asiatica, Musa acuminata, Peperomia pellucida, and Psophocarpus tetragonolobus. The extraction of TPC, tannin, flavonoid, and antioxidant activity varied significantly according to solvent polarity and plant species. The strong linear correlation found between solvent polarity index and TPC, tannin, FRAP as well as radical scavenging activity indicated solvents with increasing polarity favored the extraction of phenolic antioxidants. Plant species and extraction solvents contributed to 51.7% and 21.8% of total activity variation, respectively. C. asiatica, M. acuminata flower, and P. pellucida were best extracted with 80°C distilled water for a short duration, while methanol was preferred for P. tetragonolobus. The antioxidant index could be a potential ranking tool to identify the ideal extraction solvent for medicinal plants. Practical applications: Considering the high commercial and health-oriented values of natural phenolic antioxidants such as tannin and flavonoid, efficient extraction of these phytochemicals from different plant sources remains a challenging task due to their varying physicochemical characteristics and solubility. This study has addressed that the choice of solvents and types of plant species are critical extraction parameters for natural plant products. Comparison of tannin and flavonoid content among the different solvent extracts could reveal the ideal solvent which maximizes the extraction of phenolic antioxidants from different medicinal plants. The finding in this study may inspire nutraceutical, pharmaceutical, and cosmetic industries to re-evaluate their procedure in selecting the optimal extraction solvent and condition for different plant materials. The proposed antioxidant index in this study could serve as a potential tool to rank extraction solvents based on the antioxidant values extracted from different medicinal plants. © 2020 Wiley Periodicals LLC.