Comparative study of Pentanema verbascifolium extracts: Phytochemical composition, antioxidant potential, and enzyme inhibition across plant parts

Plants are invaluable sources of bioactive compounds with diverse therapeutic potential, yet the specific roles of various plant parts remain underexplored. This study aimed to assess the chemical composition, antioxidant activity, and enzyme inhibitory properties of methanol extracts from different parts (flower, leaf, stem, and root) of Pentanema verbascifolium obtained via ultrasound-assisted extraction. Chemical profiling revealed significant variability in phytochemical distribution, with leaves exhibiting the highest total phenolic (94.38 mg GAEs/g) and flavonoid contents (67.54 mg REs/g). Chlorogenic acid, a dominant compound, was most abundant in leaves (9739 μg/g), correlating strongly with their superior antioxidant activity. Among the antioxidant assays, leaf extracts showed the highest reducing power (Cupric Reducing Antioxidant Capacity-CUPRAC: EC 50 0.60 mg/mL; Ferric reducing antioxidant power-FRAP: EC 50 0.26 mg/mL) and radical scavenging ability (2,2-Diphenyl-1-picrylhydrazyl-DPPH: IC 50 1.35 mg/mL; ABTS: IC 50 1.28 mg/mL), supported by their highest Relative Antioxidant Capacity Index (RACI) score (1.26). Root extracts displayed notable phosphomolybdenum activity (EC 50 0.33 mg/mL) and the strongest tyrosinase inhibition (IC 50 1.16 mg/mL). Enzyme inhibition assays highlighted leaf and flower extracts as potent α-amylase inhibitors (IC 50 2.5 mg/mL), while α-glucosidase inhibition was comparable across extracts (IC 50 1.1 mg/mL). Correlation analyses identified phenolics, especially chlorogenic acid, as primary contributors to antioxidant activity, whereas flavonoids played a lesser role. These findings underscore the functional diversity of P. verbascifolium extracts, particularly the leaves, as rich sources of phenolics with potential therapeutic applications. Future studies should focus on isolating and characterizing individual bioactive compounds and evaluating their synergistic effects to enhance the understanding of their pharmacological potential.