Climate change effects on phytochemical compounds and antioxidant activity of Olea europaea

Abstract

To tolerate water shortage and high temperature, olive cv. ‘Meski’, the main variety of table olives in Tunisia, developed several biochemical changes. The hereby study focused on the adaptation of the olive tree to the climatic conditions, considering the evaluation of phenolic compounds, chlorophylls, carotenoids, saponin and steroid synthesis, as well as the evaluation of the antioxidant activity. The analyses were made upon fresh leaves collected from three coastal areas of Tunisia (North (sub-humid), center (higher semi-arid) and South (lower arid)) and using different leaves’ extracts. The results emphasized that Southern ‘Meski’ trees had leaves with more polyphenols, flavonoids, o-diphenols and tannins compared with the Northern ones. From the North to the South, ‘Meski’ leaves showed an increase of carotenoids and a decrease of chlorophyll a and b contents. The highest level of antioxidant compounds of Southern leaves could be contributed to reduce the oxidative stress of the olive tree. The spectrophotometric analysis of the antioxidant capacity of leaves collected from central and Southern areas, based on DPPH and ABTS radical-scavenging activity, showed a higher value of antioxidant activity than the Northern ones, at different extract concentrations. Therefore, the increase of the analyzed bioactive compounds can be considered as a response of the tree to surround aggressions and to oppose the oxidative stress that results from the severity of climatic conditions, characteristic of the Southern area.

Water-soluble saponins accumulate in drought-stressed switchgrass and may inhibit yeast growth during bioethanol production

“…Panax ginseng flower buds produced six unknown and four previously identified ginseng saponins commonly known as ginsenosides [ 54 ]. Olive trees that experienced drought when grown throughout the Mediterranean region accumulated saponins in their leaves [ 9 ]. Saponins are also abundant in desert plants, such as Quillaja saponaria and Yucca schidigera , which are used as commercial sources for saponin standards [ 55 , 56 ].…”

“…Many biotic and abiotic stresses trigger the generation of plant defense compounds that ensure higher plant growth and survival. Beans, olives, wild geophytes, and grasses have been found to generate compounds, such as flavonoids, alkaloids, terpenes, phenols, anthocyanins, tannins, and quinones in response to drought [ 9 – 12 ]. Osmolytes in the form of amino acids including proline, glycine, and betaine are also commonly observed in plants surviving a drought [ 13 , 14 ].…”

Potential use of wild Onobrychis species for climate change mitigation and adaptation

“…Climate change alters the concentrations of bioactive compounds to oppose the oxidative stress derived from increasing environmental tensions (Ben Mansour‐Gueddes et al., 2020). The bioactive compounds of Onobrychis species own outstanding medicinal and pharmacological properties, especially as anticancer and anti‐inflammatory drugs, in addition to its antioxidant, antibacterial, antifungal, and antiviral properties (Table 5).…”

Possible implications of climate change on the medicinal properties of Bulbine species with a particular focus on Bulbine abyssinica, Bulbine frutescens and Bulbine natalensis in South Africa

“…The increase in phenolic compounds corresponded with the increase in antioxidant activity. Netshiluvhi et al (2019) [55] analysed the antimicrobial activity of B. frutescens under temperature stress regimes of 15 and 30 °C respectively. The results showed that all the leaf extracts exhibited intermediate antimicrobial activity with MIC values ranging from 0.42 to 2.50 mg/ml across both temperature regimes, showing no statistical significant difference in the MIC values and total activity.…”