Compounds with reactive oxygen species (ROS)‐scavenging ability were studied. High‐performance liquid chromatography (HPLC) pattern of polyphenols, contents of proline and carotenoids, and antiradical (AR) capacity were determined. The malonyldialdehyde (MDA) level was also assessed. Tolerant and sensitive cotton genotypes were compared, grown in the Aegean region of Turkey at normal (field capacity) and limited (1/3 field capacity) water supply. Chlorogenic acid isomers and flavonoids were identified in HPLC pattern of polyphenols. At normal water supply, the tolerant genotype was distinguished by a higher content of all polyphenol types, higher proline, carotenoids and AR capacity and lower MDA level compared with the sensitive genotype. In plants subjected to water deficit, a decline of all polyphenol compounds, carotenoids and AR capacity was observed. However, this response was less pronounced in the tolerant than in the sensitive genotype, i.e. despite the stress conditions imposed, the tolerant plants maintained a more effective defence system. The data are corroborated by the weaker structural membrane damage in the drought‐exposed tolerant vs. sensitive genotype, according to the MDA test. Hence, diverse chemical types are involved in the non‐enzymatic ROS‐scavenging system of cotton plants and can be related to the drought tolerance of this important crop.
The flavonoid-rich natural products exert a wide range of pharmacological properties. This investigation aimed at obtaining extracts from tobacco cultivars and waste enriched with flavonoids and purified from nicotine and phenolic acids, and evaluating their radical scavenging potential. Extraction with a mixture of ethyl acetate-methanol (1:1, v/v) was employed resulting in 100% yield for flavonoids and 36% yield for phenolic acids. The crude extracts were purified using preparative column chromatography on silica gel. The content of flavonoids in the purified extracts varied from 8.8 ± 1.1% to 14.3 ± 1.8%. Nicotine was not detected in amounts higher than 0.3 μg mL(-1). The content of phenolic acids was lower than 1.0%. The radical scavenging potential of extracts from tobacco cultivars exhibited values from IC50 = 35.0 ± 3.1 to 64.6 ± 7.5 μg mL(-1). The extracts obtained by the proposed procedure are enriched with flavonoids with high radical scavenging potential and are purified from nicotine and phenolic acids. They can be regarded as potential biopharmaceuticals.
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