Abstract
The seasonal changes in the chemical composition of Olea europaea leaves from January to December at Liangshan (China) have been investigated. The highest total phenolic content (TPC), total flavonoid content (TFC), and free amino acid content (FAAC) levels were found in May and December, while the lowest levels were detected in April and September. The soluble protein content (SPC) and the soluble sugar content (SSC) were highest in spring but lowest in summer and winter. The levels of major phenolic compounds, including oleuropein, and luteolin-4’-O-glucoside, followed by apigenin-7-O-glucoside, quercetin, rutin, luteolin, and apigenin, increased during spring and winter but decreased during summer and autumn. In addition, phenolic extracts (PEs) showed dose-dependent antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and superoxide radical scavenging activity assays; the reducing power was tested. The anticancer activities of PE at various concentrations were assessed by a cell counting kit-8 (CCK-8), and the IC50 (50% effective concentration) to HEK293, HeLa, and S180 cells were 841.48, 7139, and 457.69 μg/mL, respectively. PE-treated S180 cells inhibited proliferation through activation of caspase-3/9 and disruption of the mitochondrial membrane potential. Thus, PE in Liangshan olive leaves possessed strong antioxidant and anticancer potential, and spring and winter were determined as optimal harvesting seasons.
Highlights
Olive trees (Olea europaea L.), belonging to the family Oleaceae, are one of the important economic crops all over the world [1]
The aim of this study was to investigate the seasonal variations in the chemical compositions of Liangshan olive leaves from January to December, including total phenolic content (TPC), total flavonoid content (TFC), free amino acid content (FAAC), soluble sugar content (SSC), and soluble protein content (SPC), as well as the contents of seven major phenolic compounds
S180 cells exhibited a higher sensitivity to inhibited cells only by 13.37%, and the high IC50 (7139.23 μg/mL) showed that phenolic extracts (PEs) at 0–800 μg/mL The had anti-proliferative no inhibitory effectactivity on HeLawas cellsconsistent (Table 4). with the results reported by Fares et al [53], who demonstrated that olive leaf extracts exerted anti-proliferative and pro-apoptotic effects in Jurkat cells
Summary
Olive trees (Olea europaea L.), belonging to the family Oleaceae, are one of the important economic crops all over the world [1]. Olive leaves were highly valued in Mediterranean folk medicine for the treatment of influenza, common cold, malaria, dengue, diarrhea, and surgical infections [3,7] Because of their health promoting properties, olive leaves have recently. Based on the potential health benefits, several studies have evaluated the effect of phenolic extracts (PEs) derived from olive leaves in the treatment of various diseases, such as cardiovascular diseases, cancer, myocardial oxidative damage, and atherosclerosis [13,14,15]. The aim of this study was to investigate the seasonal variations in the chemical compositions of Liangshan olive leaves from January to December, including total phenolic content (TPC), total flavonoid content (TFC), free amino acid content (FAAC), soluble sugar content (SSC), and soluble protein content (SPC), as well as the contents of seven major phenolic compounds. The potential anticancer effects of PE on human embryo kidney cells (HEK293), human cervical cancer cells (Hela), and ascites tumor cells (S180) were assessed
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