Isolation of five types of flavonol from seabuckthorn (Hippophae rhamnoides) and induction of apoptosis by some of the flavonols in human promyelotic leukemia HL-60 cells

Hippophae rhamnoides L.: A Comprehensive Review on the Botany, Traditional Uses, Phytonutrients, Health Benefits, Quality Markers, and Applications

Hippophae rhamnoides L. (sea buckthorn), consumed as a food and health supplement worldwide, has rich nutritional and medicinal properties. Different parts of H. rhamnoides L. were used in traditional Chinese medicines for relieving cough, aiding digestion, invigorating blood circulation, and alleviating pain since ancient times. Phytochemical studies revealed a wide variety of phytonutrients, including nutritional components (proteins, minerals, vitamins, etc.) and functional components like flavonoids (1-99), lignans (100-143), volatile oils (144-207), tannins (208-230), terpenoids (231-260), steroids (261-270), organic acids (271-297), and alkaloids (298-305). The pharmacological studies revealed that some crude extracts or compounds of H. rhamnoides L. demonstrated various health benefits, such as anti-inflammatory, antioxidant, hepatoprotective, anticardiovascular disease, anticancer, hypoglycemic, hypolipidemic, neuroprotective, antibacterial activities, and their effective doses and experimental models were summarized and analyzed in this paper. The quality markers (Q-markers) of H. rhamnoides L. were predicted and analyzed based on protobotanical phylogeny, traditional medicinal properties, expanded efficacy, pharmacokinetics and metabolism, and component testability. The applications of H. rhamnoides L. in juice, wine, oil, ferment, and yogurt were also summarized and future prospects were examined in this review. However, the mechanism and structure-activity relationship of some active compounds are not clear, and quality control and potential toxicity are worth further study in the future.

A Comprehensive Review on Extraction, Structure, Detection, Bioactivity, and Metabolism of Flavonoids from Sea Buckthorn (Hippophae rhamnoides L.)

Sea buckthorn (Hippophae rhamnoides L.) is an important plant with homology of medicine and food. It has rich nutritional and medicinal properties. It is used as a traditional Chinese medicine with therapeutic functions of invigorating spleen, relieving cough, eliminating food, eliminating phlegm, dispersing blood stasis, and promoting blood circulation. This review comprehensively summarized flavonoids from sea buckthorn (Hippophae rhamnoides L.), including extraction methods (solvent extraction, ultrasound-assisted extraction, microwave-assisted extraction, enzyme-assisted extraction, and collaborative extraction), two structure types (18 flavone aglycones and 81 flavone glycosides), detection methods (UV, HPLC, and NMR), bioactivities (antiviral, anti-inflammatory, hepatoprotective, weight-reducing, and hypoglycemic activities), and physiological metabolisms (most of flavonoids are converted into small molecule monophenolic acids through intestinal microbial catabolism). It will supply an important theoretical basis and valuable reference for researching and exploiting sea buckthorn (Hippophae rhamnoides L.) in the future. Practical Applications. Sea buckthorn (Hippophae rhamnoides L.) is an edible and medical plant with many functional properties. A comprehensive review on extraction, structure, detection, bioactivity, and metabolism of flavonoids from sea buckthorn (Hippophae rhamnoides L.) was made in this paper. This review will provide an important foundation for further studies of sea buckthorn (Hippophae rhamnoides L.) focusing on its development and utilization.

Pentamethylquercetin Inhibits Hepatocellular Carcinoma Progression and Adipocytes-induced PD-L1 Expression via IFN-γ Signaling

BACKGROUND

Obesity is a significant risk factor for the development of types of cancer. Programmed death 1 and its ligand programmed death-ligand 1 (PD-L1) play a crucial role in tumor immune escape. Although, the role of PD-L1 in obesity-associated hepatocellular carcinoma (HCC) remains unknown. We previously showed that the natural flavonoid pentamethylquercetin (PMQ) possesses anti-obesity properties.

OBJECTIVE

This study was designed to investigate the effects of PMQ on the development of HCC in obese mice and whether PMQ regulates PD-L1 and expression in HCC.

METHODS

Monosodium glutamate-induced obese mice were inoculated with H22 tumor cells. Tumor volumes and weights were measured. In vitro, 3T3-L1 preadipocytes were differentiated and lipid accumulation was measured by oil-red staining, and IFN-γ level was detected by Elisa. Hepatoma HepG2 cells were treated with conditional media from 3T3-L1 adipocytes (adi-CM). Western blotting was applied to detect PD-L1 protein levels in tumor tissue and HepG2 cells.

RESULTS

Compared with control mice, H22 tumors grew faster and exhibited higher PD-L1 protein levels in obese mice. PMQ inhibited H22 tumor growth and reduced PD-L1 expression in tumor tissues. PD-L1 protein level was elevated in adi-CM-treated HepG2 cells. IFN-γ was detectable in adi-CM and exogenous IFN-γ induced PD-L1 expression in HepG2 cells. PMQ affected the differentiation of 3T3-L1 preadipocytes, decreased the level of IFN-γ secreted by adipocytes and downregulated adi-CM-induced PD-L1 expression in HepG2 cells.

CONCLUSION

PMQ could inhibit HCC progression in obese mice at least in part through down-regulating adipocytes-induced PD-L1 expression via IFN-γ signaling.

Isorhamnetin Induces Cell Cycle Arrest and Apoptosis Via Reactive Oxygen Species-Mediated AMP-Activated Protein Kinase Signaling Pathway Activation in Human Bladder Cancer Cells

Isorhamnetin is an O-methylated flavonol that is predominantly found in the fruits and leaves of various plants, which have been used for traditional herbal remedies. Although several previous studies have reported that this flavonol has diverse health-promoting effects, evidence is still lacking for the underlying molecular mechanism of its anti-cancer efficacy. In this study, we examined the anti-proliferative effect of isorhamnetin on human bladder cancer cells and found that isorhamnetin triggered the gap 2/ mitosis (G2/M) phase cell arrest and apoptosis. Our data showed that isorhamnetin decreased the expression of Wee1 and cyclin B1, but increased the expression of cyclin-dependent kinase (Cdk) inhibitor p21^WAF1/CIP1, and increased p21 was bound to Cdk1. In addition, isorhamnetin-induced apoptosis was associated with the increased expression of the Fas/Fas ligand, reduced ratio of B-cell lymphoma 2 (Bcl-2)/Bcl-2 associated X protein (Bax) expression, cytosolic release of cytochrome c, and activation of caspases. Moreover, isorhamnetin inactivated the adenosine 5′-monophosphate-activated protein kinase (AMPK) signaling pathway by diminishing the adenosine triphosphate (ATP) production due to impaired mitochondrial function. Furthermore, isorhamnetin stimulated production of intracellular reactive oxygen species (ROS); however, the interruption of ROS generation using a ROS scavenger led to an escape from isorhamnetin-mediated G2/M arrest and apoptosis. Collectively, this is the first report to show that isorhamnetin inhibited the proliferation of human bladder cancer cells by ROS-dependent arrest of the cell cycle at the G2/M phase and induction of apoptosis. Therefore, our results provide an important basis for the interpretation of the anti-cancer mechanism of isorhamnetin in bladder cancer cells and support the rationale for the need to evaluate more precise molecular mechanisms and in vivo anti-cancer properties.