MEDICINAL PLANTS’ STRESS FACTORS: EFFECTS ON METABOLITES AND NOVEL PERSPECTIVES FOR TOLERANCE

Medicinal plants are rich in secondary metabolites representing different chemical classes and synthesized by various biochemical pathways. However, these compounds are susceptible to potential herbal predators and to environmental influences. Several factors induce different biotic and abiotic stresses (drought, cold, salinity, heat) that lead to fluctuations in the biogenesis and accumulation of secondary metabolites by which plants react to overcome the threatening stress conditions. This contribution aims to give an overview of the various medicinal plant defense mechanisms against imminent threats and their impact on secondary metabolites profiles in the most effective medicinal plant species such as the levels of vincristine in Catharanthus roseus which is affected by salinity and drought stress, sage (Salvia officinalis) that showed fluctuations in terpenes level under drought stress and mineral contents in the soil and Papaver somniferum that exhibited a decrease in alkaloids content under cold stress. From a wider perspective, the aim of this study is to present novel tools and strategies used for the preservation of some plant species from extinction by minimizing as much as possible the risk of exogenous influences on phytochemicals levels and on plant bio genome and manipulating the stress factors to ensure plants quality and safety. It also aims to raise awareness about the consumption of herbal medicines without respecting the herbal monographs information about the safe dose, the interactions with drugs, and the side effects, in addition to the necessity of performing toxicity studies by pharmaceutical industries, especially on herbal medicines raised under various stress factors because of the risk of SMs (secondary metabolites) accumulation in these plants at a critical level that may be toxic to consumers

GENUS MELALEUCA: PHYTOCHEMISTRY, PHARMACOLOGY AND EFFECT AGAINST COVID-19

Medicinal plants are used for the prevention and treatment of many diseases as they are rich in phytochemical constituents (like terpenes, flavonoids, and alkaloids) responsible for the pharmacological effects of these plants. Genus Melaleuca named the tea tree, belonging to the family Myrtaceae, is cultivated in Australia as well as in the Pacific and some regions of Asia. It has been employed in Australian traditional medicine for its broad antimicrobial activity because of its contents of phenolic compounds, monoterpenes, tannins, flavonoids, sesquiterpenes, and essential oils. Owing to the valuable uses of plants of genus Melaleuca, for different medical purposes, it was deemed interest to summarize the previous studies reported from 2004 to 2020 in the available literature about the phytochemistry and pharmacological potential of both volatile and non-volatile components of Melaleuca species. Accordingly, this article may help researchers work on plants of genus Melaleuca to promote clinical applications towards the development of novel drugs of diverse pharmacological activities, including inhibitory effects on COVID 19 obtained from Melaleuca species