Antioxidant and Antibacterial Activities of Hybrid, White and Orange Hibiscus (Hibiscus Rosa-Sinensis)

Chai, Yi Tong (2020) Antioxidant and Antibacterial Activities of Hybrid, White and Orange Hibiscus (Hibiscus Rosa-Sinensis). Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Hibiscus rosa-sinensis, distributed throughout tropics and subtropics, is useful for various purposes like foods, beverages and therapeutics. This study aims to determine the antioxidant activity and antibacterial activity of three types of hibiscus (white, orange and hybrid hibiscus). Analyses were done on the flowers and leaves using two extraction solvents. The antioxidant analysis was carried out using DPPH radical scavenging activity, total phenolic compound (TPC), total flavonoid content (TFC) and ferric reducing antioxidant power (FRAP) assays. The antibacterial test was carried out by disc diffusion method. Results showed that orange flower had the highest antioxidant activity when compared to hybrid and white flower in terms of DPPH, TPC and FRAP. Orange flower had 90.45% radical scavenging activity, 33.06 mg GAE/g of DW for TPC and 125.38 mg FE/g of DW for FRAP. Among the three different types of leaf, leaves of hybrid hibiscus showed the highest TFC (27.75 mg CE/g of DW). For the antibacterial test, hybrid flower showed the largest inhibition zone (18.67 mm) for Staphylococcus aureus, while orange flower showed the largest inhibition zone (16.00 mm) for Escherichia coli. Methanol was found to be a good extraction solvent for DPPH, FRAP and TFC whereas ethanol was a good extraction solvent for TPC. In conclusion, flowers exhibited higher antioxidants activity than leaves whereas leaves contain higher flavonoids than flowers. For the antibacterial test, the zone of inhibition is higher against gram positive bacteria when compared to gram negative bacteria. Orange hibiscus flower with relatively high antioxidant activity had potential use as functional ingredient in food products and possibly as therapeutic agent. Keywords: Hibiscus rosa-sinensis, antioxidant activity, antibacterial activity.