Influencing the Contents of Secondary Metabolites in Spice and Medicinal Plants by Deliberately Applying Drought Stress during Their Cultivation

Abstract

Medicinal plants grown under semi-arid conditions generally reveal significantly higher concentrations of relevant natural products than identical plants of the same species, which are cultivated in moderate climates. So far, there is very limited information on this well-known phenomenon. In the present study, corresponding data are compiled and relevant aspects are discussed. It turns out that metabolic reactions triggered by drought stress are responsible for the higher natural product accumulation in plants grown in semi-arid regions. The related plant physiological and biochemical background can be summarized as follows: In plants suffering drought stress, the water shortage caused by limited water supply triggers stomata closure. As a result, the uptake of CO 2 is markedly decreased and the consumption of reduction equivalents (NADPH+H +) consumed in the course of CO 2-fixation via Calvin cycle declines considerably, generating a massive oversupply of NADPH+H +. Consequently, all metabolic processes are pushed towards the synthesis of highly reduced compounds, such as isoprenoids, phenols or alkaloids. Based on these considerations, impulses for novel practical approaches for enhancing the product quality by deliberately applying drought stress during the cultivation of medicinal plants are outlined. However, as drought stress concomitantly also leads to massive reductions in biomass production, special emphasis must be put on the interference of these stress related effects.

The Comparative Studies of the Phytochemical Levels and the in vitro Antioxidant Activity of Tridax procumbens L. from Different Habitats

“…The increased level of flavonoids in the hilly terrains is in agreement with Monschein et al, who found that the environmental factors at higher altitude result in the elevated levels of flavonols. 36 The observation that the dry-land, flavonoid content is higher than in the wet-land is in line with Al-Gabbiesh et al, 37 who reported that plants exposed to drought stress indeed reveal higher concentrations of secondary metabolites than those cultivated under well watered conditions. Drought stress without any change in the enzyme activity, but promote the rate of synthesis of the highly reduced secondary plant products, such as isoprenoids, phenols ( flavonoids) alkaloids and tannins.…”

Water deficit‐induced oxidative stress affects artemisinin content and expression of proline metabolic genes in Artemisia annua L.

“…Drought is one of the most serious environmental stresses that adversely affect plant growth and development . Plants overcome water stress in part by producing secondary metabolites, which are compatible solutes, free‐radical scavengers, and transpiration reducers that protect cells from environmental stresses such as water deficit . Artemisinin is a notable secondary metabolite because it is an antimalarial drug isolated from Artemisia annua L., one of the top 10 medicinal crops of the New World .…”

The Environmental Fluctuations of some Bioactive Nutraceutical Compounds in Zilla spinosa Inhabiting Arid Habitats

“…Seasonal variation was pronounced in different secondary metabolites content of Zilla inhabiting wadi Hagul. The environmental stressors pushed all metabolic processes towards the synthesis of secondary metabolites as isoprenoids, phenols, flavonoids or alkaloids due to the closure of stomata and consequently reduction in the endogenous CO2 level and the consumption of reduction equivalents (NADPH + H + ) utilized in the CO2-fixation via Calvin cycle (Ramakrishna and Ravishankar, 2011;Al-Gabbiesh et al, 2015).…”