Variation of Secondary Metabolites, Chlorophyll Contents, and Antioxidant Activity in Six Medicinally Important Plants in Bangladesh

Plant phenolics and flavonoids function as antioxidants that act as scavengers of free radicals in the human body. This study aimed to determine the total phenolics and flavonoids contents, ferric-reducing antioxidant power (FRAP), free radical scavenging ability, chlorophyll contents, and total amounts of carotenoids of six medicinal plants viz. Anisomeles indica (L.) Kuntze, Eclipta prostrata (L.) L., Glinus oppositifolius (L.) Aug.DC., Litsea glutinosa (Lour.) C.B.Rob., Origanum vulgare L., and Oxalis debilis Kunth. The results reveal that L. glutinosa has the maximum amount of total phenolic content (TPC) (1.906 mg GAE g-1 FW) and total flavonoid content (TFC) (13.933 mg QUE 100g-1 FW), while the lowest TPC (0.2803 mg GAE g-1 FW) was observed in O. vulgare and the least TFC (1.6 mg QUE 100g-1 FW), was observed in A. indica. The leaves of L. glutinosa showed excellent antioxidant properties (IC50 = 6.24 mg mL-1), and G. oppositifolius showed the least antioxidant potential (IC50 =18.423 mg mL-1). Pigment content such as chlorophyll-a was highest in E. prostrata (1.5963 mg g-1), while L. glutinosa has the highest chlorophyll-b (2.176 mg g-1 FW), chlorophyll-(a+b) (3.6157 mg g-1 FW), and carotenoids (1.61 µg 100g-1 FW) content. A strong linear correlation (DPPH, R2 = 0.8688, FRAP, R2 = 0.8595) was found between TPC and antioxidative capability. L. glutinosa contains significant amounts of phenols and flavonoids, which have antioxidant qualities, suggesting the possibility of using this species in phytotherapy and pharmacy.