Altitudinal Variation in the Antioxidant Potential of Tinospora cordifolia (Willd.) Hook. F. & Thomson Stem Extracts from Himachal Pradesh, Western Himalaya: A DPPH– and ABTS– Based Comparative Study

Tinospora cordifolia (Menispermaceae), the Ayurvedic Rasayana herb Guduchi, is widely used across the Himalayan foothills, yet how growing altitude shapes its free-radical scavenging capacity is not well resolved.Stem material was collected from four populations along a 328-1,453 m altitudinal transect in Una, Hamirpur, and Mandi districts of Himachal Pradesh (coded CP01-CP04 corresponding to Amb, Bhota, Sundernagar, and Karsog respectively), and methanolic Soxhlet extracts were evaluated for antioxidant activity using DPPH and ABTS radical scavenging assays, with IC₅₀ values (mean ± SEM) determined by an independent testing laboratory.In the DPPH assay, Sundernagar (1,140 m; IC₅₀ = 5.694 ± 0.01 µL mL⁻¹) and Bhota (867 m; IC₅₀ = 7.592 ± 0.03 µL mL⁻¹) outperformed the ascorbic acid standard (IC₅₀ = 7.844 ± 0.02 µg mL⁻¹), while Karsog (1,453 m; 13.77 ± 0.03 µL mL⁻¹) and Amb (328 m; 15.84 ± 0.02 µL mL⁻¹) did not.In the ABTS assay, all four populations outperformed the ascorbic acid standard (IC₅₀ = 20.19 ± 0.02 µg mL⁻¹), with potency ranked Sundernagar (3.161 ± 0.06) > Bhota (3.399 ± 0.01) > Karsog (3.527 ± 0.03) > Amb (5.355 ± 0.02 µL mL⁻¹).The two assays agreed on an identical overall potency ranking : Sundernagar > Bhota > Karsog > Amb.Only the lowest-altitude population (Amb) was consistently the least potent in both assays; the highest-altitude population (Karsog) was not the most potent in either assay, and the relationship between altitude and antioxidant potency was not monotonic.These findings support Sundernagar-and Bhota-sourced T. cordifolia stem as comparatively potent raw material for antioxidant-oriented pharmaceutical and nutraceutical formulation, while indicating that altitude alone does not reliably predict antioxidant potency across these four populations, highlighting the need for a larger population sample to clarify the relationship.