Phytotoxic analysis of coastal medicinal plants and quantification of phenolic compounds using HPLC

Abstract

Medicinal plants are rich sources of bioactive phytochemicals. Production of such chemicals usually increased under unfavorable conditions. This study investigated the phytotoxic potential of 105 medicinal plants distributed in arid/semiarid areas along Arabian Sea coast of Pakistan. Total polyphenols, flavonoids, tannins and composition of individual phenolic compounds were also determined in species which showed high phytotoxic potential. Sandwich method was used to determine the phytotoxicity of medicinal plants on the growth of lettuce seedlings. Radicle growth was inhibited more than the hypocotyl growth. In general, halophytes showed higher phytotoxic potential than non-halophytes. Capparis cartilaginea, Indigofera hochstetteri, Parkinsonia aculeata and Prosopis glandulosa showed highest degree of inhibition. Higher amount of total phenols (16.35–25.33 mg GAE g−1), flavonoids (3.32-6.41 mg QE g−1) and tannins (1.54–2.54 mg TAE g−1) were found in these species. Pyrocatechol, quercetin, gallic, hydroxybenzoic and ferulic acids were detected as major phytotoxins, of which, gallic acid, pyrocatechol and quercetin were most abundant. These phytochemicals could be used for the production of natural, safe, healthy and eco-friendly agro-chemicals. Furthermore, these plants can be grown without encroaching agricultural lands, and can convert vast areas of arid/saline lands into economically viable resources, which also helps to halt climate change and desertification.