Olive (Olea europaea) leaf, an important traditional herbal medicine, displays cardioprotection that may be related to the cellular redox modulating effects of its polyphenolic constituents. This study was undertaken to investigate the protective effect of the ethanolic and methanolic extracts of olive leaves compared to the effects of oleuropein, hydroxytyrosol, and quercetin as a positive standard in a carbonyl compound (4-hydroxynonenal)-induced model of oxidative damage to rat cardiomyocytes (H9c2). Cell viability was detected by the MTT assay; reactive oxygen species production was assessed by the 2',7'-dichlorodihydrofluorescein diacetate method, and the mitochondrial membrane potential was determined using a JC-1 dye kit. Phospho-Hsp27 (Ser82), phospho-MAPKAPK-2 (Thr334), phospho-c-Jun (Ser73), cleaved-caspase-3 (cl-CASP3) (Asp175), and phospho-SAPK/JNK (Thr183/Tyr185) were measured by Western blotting. The ethanolic and methanolic extracts of olive leaves inhibited 4-hydroxynonenal-induced apoptosis, characterized by increased reactive oxygen species production, impaired viability (LD50: 25 µM), mitochondrial dysfunction, and activation of pro-apoptotic cl-CASP3. The ethanolic and methanolic extracts of olive leaves also inhibited 4-hydroxynonenal-induced phosphorylation of stress-activated transcription factors, and the effects of extracts on p-SAPK/JNK, p-Hsp27, and p-MAPKAPK-2 were found to be concentration-dependent and comparable with oleuropein, hydroxytyrosol, and quercetin. While the methanolic extract downregulated 4-hydroxynonenal-induced p-MAPKAPK-2 and p-c-Jun more than the ethanolic extract, it exerted a less inhibitory effect than the ethanolic extract on 4-hydroxynonenal-induced p-SAPK/JNK and p-Hsp27. cl-CASP3 and p-Hsp27 were attenuated, especially by quercetin. Experiments showed a predominant reactive oxygen species inhibitory and mitochondrial protecting ability at a concentration of 1-10 µg/mL of each extract, oleuropein, hydroxytyrosol, and quercetin. The ethanolic extract of olive leaves, which contains larger amounts of oleuropein, hydroxytyrosol, verbascoside, luteolin, and quercetin (by HPLC) than the methanolic one, has more protecting ability on cardiomyocyte viability than the methanolic extract or each phenolic compound against 4-hydroxynonenal-induced carbonyl stress and toxicity.

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Phytochemical investigations of Taxus baccata L. by successive chromatographic methods resulted in the isolation of the lignans lariciresinol (1), taxiresinol (2), 3´-demethylisolariciresinol- 9´-hydroxyisopropylether (3), isolariciresinol (4), and 3-demethylisolariciresinol (5) as well as taxoids. Compounds 1 - 5 were evaluated for their acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and lipoxygenase (LOX) inhibitory activities, which play a role in the pathogenesis of Alzheimer’s disease (AD), by in vitro spectrophotometric methods, while they were also screened for their antioxidant capacity in 2,2-diphenyl-1- picrylhydrazyl (DPPH) radical scavenging, ferrous ion-chelating effect, and ferric-reducing antioxidant power (FRAP) at 125, 250, 500, and 1000 μg ml-1. All compounds exhibited a moderate inhibition against both BChE and LOX, whereas they were inactive towards AChE. The compounds displayed a great scavenging activity against DPPH especially at 500 and 1000 μg ml-1. Besides, they were found to exert noteworthy reducing antioxidant power on ferric ions. In particular, the FRAP of compounds 2 (3.552 ± 0.02), 4 (3.021 ± 0.71), and 5 (3.533 ± 0.01) were as high as that of the reference chlorogenic acid (3.618 ± 0.01) at 1000 μg ml-1. None of the compounds exhibited chelating ability against ferrous ions.