Chemotypic Variation in Antioxidant Activity and Phytochemical Profiles of Terminalia arjuna (Roxb. ex DC.)

Abstract

Terminalia arjuna (Roxb. ex DC.) Wight & Arn. is a medicinal tree widely used in South Asian traditional medicine for cardioprotection, primarily attributed to its antioxidant phytochemicals. However, the phytochemical profile of T. arjuna growing in Sindh, Pakistan where arid climate and saline soils may induce unique chemotypic variation remains uncharacterized. This study compared the phytochemical composition and in vitro antioxidant capacity of aqueous and methanolic extracts from leaves, stem bark and seeds of T. arjuna collected from Sindh, Pakistan. Plant material was extracted with distilled water and 80% methanol. Qualitative phytochemical screening (flavonoids, alkaloids) and quantitative analyses (total phenolic content; total antioxidant capacity via phosphomolybdenum assay; proteins, carbohydrates, reducing sugars) were performed (n=3 biological replicates). Statistical analysis used t-tests, two-way ANOVA and Pearson correlation (α=0.05). Flavonoids and alkaloids were present in all extracts. The aqueous leaf extract showed significantly higher TPC (49.8 ± 3.5 mg GAE/g) and TAC (38.4 ± 3.1 mg AAE/g) than its methanolic counterpart (p<0.001 and p<0.01, respectively), with a strong positive correlation (r=0.94, p<0.001). The methanolic seed extract contained the highest protein concentration (16.8 ± 1.5 mg/g). Significant variation was observed across plant parts and solvents (two-way ANOVA: plant part F(2,12)=45.32, p<0.001; solvent F(1,12)=38.76, p<0.001; interaction F(2,12)=12.45, p<0.001). This study establishes the first phytochemical baseline for Sindh-grown T. arjuna, confirming chemotypic variation. The aqueous leaf extract is a potent, renewable, sustainable antioxidant source, offering an ecologically responsible alternative to destructive bark harvesting.