Comparative Phytochemical Allelopathic Activity of Leaf and Flower Oleoresin from Adhatoda vasica L.

Abstract

The Acanthaceae family includes several medicinally important species, notably Adhatoda vasica, which is widely used in traditional medicine for respiratory and inflammatory disorders due to its rich phytochemical profile. The study presents a comparative phytochemical and allelopathic analysis of leaf (AVLO) and flower (AVFO) oleoresins from Adhatoda vasica L. (Acanthaceae), a widely utilized medicinal plant. Methanolic extracts were prepared via cold percolation and characterized using gas chromatography–mass spectrometry (GC–MS). A total of forty-nine phytoconstituents were identified, representing 80.43% of the total peak area in AVLO, and 82.22% in AVFO. The major identified compounds included antipyrine (30.91%) in AVLO, while 5-hydroxymethylfurfural (24.24%) in AVFO. However, the presence of certain compounds (e.g., clindamycin, antipyrine) requires confirmation through co-injection with authentic standards or alternative analytical methods, as these may arise from library matching errors or contamination. The allelopathic potential of both oleoresins was evaluated through seed germination bioassays against Raphanus raphanistrum subsp. sativus, revealing significant, dose-dependent inhibition. IC₅₀ values for seed germination (AVLO: 140.81±24.19 µL/mL; AVFO: 154.79±14.48 µL/mL), root length, and shoot length confirmed notable phytotoxic activity, with AVLO exhibiting marginally greater potency for seed germination inhibition, whereas AVFO showed greater potency for root and shoot length inhibition. These findings underscore the potential of A. vasica oleoresins as natural bioherbicides, though further validation through compound isolation, field trials, and toxicological assessments is required before practical application.