Phytochemical screening, total phenolic content and free radical scavenging activity of Bruguiera sexangula and Connarus semidecandrus extracts in Kung Krabaen Bay.

Phytochemical investigation of Bruguiera sexangula (Lour.) Poir and Connarus semidecandrus Jack, medicinal plants found in mangrove forest of Thailand, revealed the presence of tannin, terpenoids, saponins, flavonoids, alkaloids, and anthraquinones in various plant parts. The total phenolic content was determined by Folin-Ciocalteu assay, expressed in gallic acid equivalent (mg of GAE/g of extract). The free radical scavenging activity was estimated as IC ₅₀ values using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) methods. The result showed high phenolic content, varying from 350 to 465 mg GAE/g extract. The highest level of total phenolic content was found in the leaves (464.7 ± 0.4 mg GAE/g) followed by the branches (443.4 ± 0.4 mg GAE/g) of B. sexangula extracts. The strongest free radical scavenging activity was exerted by extracts of branches of B. sexangula with IC₅₀ of 8.62 ± 0.37 µg/mL (DPPH) and 167.90 ± 18.13 mmol Fe²⁺ equivalent/gram extract of leave using FRAP method. This study confirmed that medicinal plants with high phenolic content could possess strong free radical scavenging property thus indicated that the methanolic extracts of B. sexangula and C. semidecandrus could be significant sources of natural antioxidant.

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