Phytochemical analysis, in vitro screening of antioxidant and antibacterial potential of Cajuput (Melaleuca cajuputi) extract against pathogenic Vibrio spp.

Cajuput (Melaleuca cajuputi) has been used as a form of herbal treatment. This study is aimed at evaluating the phytochemical constituents as well as the antioxidant and antibacterial activities of ethanol extract (MLE) and aqueous extract (MLW) of M. cajuputi leaves. Preliminary phytochemical screening was performed using colour-forming standard methods. The total phenolic content (TPC), total flavonoid content (TFC), and total condensed tannins (TCT) were determined using the Folin-Ciocalteu, aluminum chloride, and vanillin methods, respectively. The antioxidant activity was evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assays. The inhibition zone of antibacterial activity using the disc diffusion method with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of extracts were performed using the microdilution method. The results showed that the TPC, TFC, and TCT of MLW were higher than those of MLE (p < 0.05). The MLW also showed higher antioxidant activity than MLE (p < 0.05), with the IC50 values of DPPH and ABTS radical scavenging activity at 0.078 mg/mL and 0.193 mg/mL, respectively. For antibacterial activity, MLW exhibited a higher zone of inhibition against Vibrio harveyi (7.94 mm) and Vibrio parahaemolyticus (7.65 mm) than MLE. All extracts were effective against both types of pathogenic bacteria, with MIC and MBC of 6.25 mg/mL and 25 mg/mL, respectively. The study concludes that the aqueous extract of M. cajuputi possesses better antioxidant activity than the ethanol extract and can be used to control the pathogenic Vibrio spp.