The antibacterial and antioxidant activities of plumbagin-rich methanolic root extracts from Plumbago zeylanica L.

Abstract

Plumbago zeylanica L. (Family: Plumbaginaceae) is a perennial shrub that primarily grows in wild habitats and is recognized for its various therapeutic potentials. This study compared the plumbagin contents of different plant parts (leaf, stem, and root) of P. zeylanica collected from four districts (Bankura, Nadia, Hooghly, and Bardhaman-Purba) in West Bengal. It demonstrated the superiority of root extracts, which had the highest yield (mg/g extract) in Bankura (50.79 ± 4.58), followed by Bardhaman-Purba (47.26 ± 3.61), Nadia (32.79 ± 0.58), and Hooghly (25.99 ± 0.58). The plumbagin-rich root extracts were further characterized, and comparative estimations were conducted using TLC, UV-Vis scan, and HPLC analyses, confirming the results obtained from the initial spectrophotometric method. The antioxidant activities of the root extracts showed the highest efficacy in Hooghly (TAA: 123.05 ± 7.79 mg AAE/g; FRAP: 9.45 ± 0.60 mM Fe²⁺/mg; DPPH IC₅₀: 250.29 ± 14.33 µg/ml and ABTS IC₅₀: 84.90 ± 9.72 µg/ml), while root extracts from Bankura exhibited the highest antibacterial activities (IZ: 28.13 ± 1.04 mm; MIC: 0.11 ± 0.01 mg/ml and MBC: 0.13 ± 0.02 mg/ml). Pearson correlation analyses identified a significant relationship between antibacterial activities and plumbagin content, whereas the antioxidative properties had no such correlation with plumbagin. Furthermore, the UPGMA cluster analysis distinguished the four districts based on their root-specific bioactivities and plumbagin content. The findings highlighted the root extracts' potent antioxidative and antibacterial properties, emphasizing plumbagin's unique role in antibacterial efficacy.