Impacts of Habitat Change on Phytochemistry and Antimicrobial activities in selected medicinal plants of rocky areas of Sindh

Abstract

Sindh has three mountain ranges which differ in their topography and climate. Plants that grow on all three ranges face different edaphic and climatic factors. This study focused on seven medicinal species and was designed to determine whether plants' metabolic profiles and antimicrobial activity collected from six different localities and/or different seasons differed in their metabolic profiles. The plant samples were collected during spring (February-March) and summer (July-August) from six geographical locations with rocky habitats. The seven plants were: “Aerva javanica, Calotropis procera, Capparis decidua, Cassia senna, Fagonia indica, Leptadenia pyrotechnica , Salvadora oleoides” each collected from six locations, i.e., Karachi, Jamshoro, Johi, Dadu, Gorakh Hill, Rohri and Karoonjhar. The samples were collected by uprooting the whole plant, and soil samples were taken from the rhizosphere of each plant collected. About 20 samples of each species from each location were collected and combined to develop a composite sample. Total 20 elements (Al; As; B; Ba; Cd; Cr; Cu; Fe; Hg; K; Mg; Mn; Na; Ni; Pb; Rb; Sr; Ti; V and Zn) from each soil and plant sample were detected. The Fe was the highest concentration in soil at all locations. Besides Fe, the soil samples showed high K, Mg, Na, and Hg concentrations from different locations. Soil mineral concentrations increased progressively at Jamshoro, Johi (Dadu) to Karoonjhar. Plant collections showed K, Na, Mg, Fe, and Hg as frequently occurring elements from all locations during both seasons; however, K and Na were the most abundant elements. Seasonally, K was found higher than all elements during spring, while Na in summer was higer followed by K in all samples. Most of the elements in plants were found in significantly higher concentrations during spring, while the same elements were, with some exceptions, in lower concentration during summer. Each medicinal plant showed significantly different phenol contents during summer and spring at all locations. The highest total phenols and flavonoids were observed in Calotropis procera Br during and Cassia senna L during summer, respectively, at Johi. The highest total alkaloids were observed in Cassia senna during summer at Jamshoro. The highest total Tannins were observed in plant Capparis decidua during summer at Rohri. The antioxidant activity of Capparis decidua during summer from at Karoonjhar was significantly higher than all plants samples. The extracts of Capparis decidua at Rohri collected during summer were most effective against Escherichia coli. The highest antibacterial activity against Staphylococcus aureus was found in methanol extracts of Aerva javanica collected from Gorakh during the summer. The Aspergillus niger was found most sensitive to the extracts of Salvadora oleoides collected from Karachi during the summer. Samples collected in summer from all of the locations had higher concentrations of the elements and secondary compounds examined as well as a greater antimicrobial activity than those collected in spring. Hence, it is recommended that the medicinal plants collected during summer.