Effect of seasonal variations on phytoconstituents and antimicrobial properties of Holoptelea integrifolia, an important medicinal plant from Kangra District in Himachal Pradesh, India: A case study

Medicinal plants have been used for the treatment of many ailments since time immemorial. The pharmacological significance of these plants is attributed to the presence of secondary metabolites which are greatly affected by the changes in the climatic conditions. This study investigates the effect of seasonal variations on the phytochemical constituents and biological activities of Holoptelea integrifolia leaves and bark in Kangra district, Himachal Pradesh, India. The antimicrobial activity and minimum inhibitory concentration of various plant extracts were determined using agar well diffusion and resazurin dye methods. The qualitative and quantitative analysis of phytochemical, besides antioxidant activity, were compared in all samples during different seasons. The experimental results revealed that the chloroform extracts of leaves and bark of plants during winter season were most effective against S. flexneri with highest zone of inhibition (ZOI) of 19.5±0.12mm and 22.6 ±0.32mm at 4 mg/40 μμl, respectively. However, MIC of leaf and bark extracts in case of S. flexneri were 0.3125 mg/100 μl and 0.0781 mg/100 μl, respectively. Phytochemical analysis of H. integrifolia confirmed significant seasonal variation, with phenols, flavonoids and terpenoids highest in the winter season, while alkaloids dominated in autumn season. The chloroform extract of H. integrifolia leaves and bark exhibited highest antioxidant activity in DPPH assay (78.81±0.12% & 81.41±0.24%) followed by H2O2 and phosphomolybdenum at 300μg/ml conc. respectively. The results of the present work revealed that the bark of H. integrifolia during winter season exhibited better antimicrobial activity than the leaves, providing a valuable basis for the future efforts in developing novel herbal drugs.