The effects of Kaempferol and its Glycosides on MDA Formation and the Activity of some Enzymes in In Vitro and In Vivo studies

Oxidative stress (OS) is a pathological state that develops when there is a disequilibrium between the generation and accumulation of reactive oxygen species (ROS) in cells and tissues and the capacity of biological systems to detoxify these reactive intermediates. Free radicals, mainly formed from unsaturated fatty acids during lipid peroxidation, act as secondary messengers in oxidative and electrophilic stress responses by transmitting electrophilic signals. They also influence vital cellular pathways, including autophagy, proliferation, and apoptosis. Considering the harmful consequences of OS, the present study examined the effect of the flavonoid kaempferol on malondialdehyde (MDA) formation and the activities of major antioxidant enzymes—catalase, glutathione peroxidase (GPx), and glutathione reductase (GR)—in rat brain tissue homogenates exposed to oxidative stress. Moreover, the in vivo impact of kaempferol and its glycosides (kaempferol-7-O-rhamnoside, kaempferitrin, and afzelin) on NADH dehydrogenase activity in rat brain mitochondria was also evaluated. The findings revealed that kaempferol exhibited potent antioxidant activity under OS conditions. It significantly enhanced GPx and GR activities while lowering MDA levels, a key lipid peroxidation byproduct that accumulates during oxidative stress. Kaempferol also restored catalase activity, which was markedly reduced under OS. Specifically, kaempferol decreased MDA accumulation by 1.61-fold and increased catalase activity by 3.3-fold. Additionally, GPx and GR activities, which had been substantially reduced by OS, were recovered to 77.16% and 63.13% of control levels, respectively. Kaempferol also showed strong inhibitory effects on mitochondrial NADH dehydrogenase activity, achieving complete inhibition at 50 μM. Its glycosides exhibited lower but significant inhibition, with kaempferol-7-O-rhamnoside reducing activity by 84.34 ± 0.96%, kaempferitrin by 61.58±1.9%, and afzelin by 47.64±1.6%. The overall order of inhibitory potency was: kaempferol > kaempferol-7-O-rhamnoside > kaempferitrin > afzelin.

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