Phytochemical Screening and Antioxidative Potentials of Plectranthus Amboinicus Leaves Extract

Abstract Oxidative stress, resulting from an imbalance between reactive oxygen species (ROS) and the body’s antioxidant defense system, plays a critical role in the development of non-communicable diseases (NCDs) such as cardiovascular disease, diabetes, and cancer. These diseases are increasingly prevalent in Malaysia, contributing significantly to national morbidity and mortality. While synthetic antioxidants are widely used, their potential health risks have prompted an increased interest in safer, plant-derived antioxidants as alternatives. Plectranthus amboinicus, also known as Cuban oregano, or pokok bangun-bangun, is traditionally used to treat respiratory conditions, digestive disorders, and fever. Although the plant’s biological activities are widely studied, there is still limited research done on the P. amboinicus plant from Malaysia. This study aimed to investigate the phytochemical constituents and antioxidant activity of P. amboinicus leaves collected in Terengganu, Malaysia. In this study, the crude methanol and aqueous P. amboinicus extract were prepared using a combination of maceration and ultrasound-assisted extraction techniques. Then, phytochemical screening, total phenolics, and total flavonoids content were conducted to identify bioactive substances. The antioxidant activity of the leaves was assessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assay. Findings revealed the presence of flavonoid, phenolic, coumarin, and cardiac glycoside in the extract. Quantitative analysis demonstrated that the methanol extract exhibited higher flavonoid (21.27 ± 4.85 mg QE/g) and phenolic content (59.96 ± 18.48 mg GAE/g) when compared to the aqueous extract. The DPPH scavenging activity is also significantly higher in the methanol extract, with the IC50 of 76.23 ± 32.74 μg/ml when compared to the aqueous extract (112.04 ± 45.02 μg/mL). Similar trends were observed in FRAP assay, with the value of 0.38 ± 0.025 mM Fe2+/g extract for methanol and 0.31 ± 0.13 mM Fe2+/mg extract for aqueous, respectively. The study highlighted the presence of a significant amount of phenolics and flavonoids in the extract, emphasizing their significant impact on the antioxidant properties of P. amboinicus extract. In conclusion, P. amboinicus exhibits antioxidant activity and has the potential to be used as a natural antioxidant. Keywords: Plectranthus amboinicus, Phytochemicals, Total Flavonoid, Total Phenolic, Antioxidant.