In recent years, a number of natural products isolated from Chinese herbs have been found to inhibit proliferation, induce apoptosis, suppress angiogenesis, retard metastasis and enhance chemotherapy, exhibiting anti-cancer potential both in vitro and in vivo. This article summarizes recent advances in in vitro and in vivo research on the anti-cancer effects and related mechanisms of some promising natural products. These natural products are also reviewed for their therapeutic potentials, including flavonoids (gambogic acid, curcumin, wogonin and silibinin), alkaloids (berberine), terpenes (artemisinin, β-elemene, oridonin, triptolide, and ursolic acid), quinones (shikonin and emodin) and saponins (ginsenoside Rg3), which are isolated from Chinese medicinal herbs. In particular, the discovery of the new use of artemisinin derivatives as excellent anti-cancer drugs is also reviewed.
Salvia miltiorrhiza Bunge (Danshen in Chinese) is a classical Huoxue Huayu (a traditional Chinese medical term means promoting blood circulation and removing blood stasis) herb with 1000 years of clinical application. It mainly contains two groups of ingredients: the hydrophilic phenolic acids and the lipophilic tanshinones. Both groups have demonstrated multiple bioactivities, such as antioxidative stress, antiplatelet aggregation, anti-inflammation, among others. Recent data have demonstrated that its lipophilic compounds, especially the tanshinones, show potent anticancer activities both in vitro and in vivo. The anticancer effects of the hydrophilic phenolic acids have also been reported. Furthermore, tanshinones provide structural skeletons for chemical modifications, allowing for a series of derivatives of interests. This review provides a systematic summary of the anticancer profile and the underlying mechanisms of the bioactive compounds isolated from Danshen with special emphasis on tanshinones, aiming to bring new insights for further research and development of this ancient herb.
Cucurbitacin and its derivatives (cucurbitacins) are a class of highly oxidized tetracyclic triterpenoids. They are widely distributed in the plant kingdom, where they act as heterologous chemical pheromones that protect plants from external biological insults. Their bioactivities first attracted attention in the 1960s. Documented data demonstrate that cucurbitacins possess strong pharmacological properties, such as antitumor, anti-inflammatory, and hepatoprotective effects, etc. Several molecular targets for cucurbitacins have been discovered, such as fibrous-actin, signal transducer and activator of transcription 3, cyclooxygenase-2, etc. The present study summarizes the achievements of the 50 years of research on cucurbitacins. The aim was to systematically analyze their bioactivities with an emphasis on their anticancer effects. Research and development has shed new insight into the beneficial properties of these compounds.
Accumulating clinical evidence suggests that hyperuricemia is associated with an increased risk of type 2 diabetes. However, it is still unclear whether elevated levels of uric acid can cause direct injury of pancreatic β-cells. In this study, we examined the effects of uric acid on β-cell viability and function. Uric acid solution or normal saline was administered intraperitoneally to mice daily for 4 weeks. Uric acid-treated mice exhibited significantly impaired glucose tolerance and lower insulin levels in response to glucose challenge than did control mice. However, there were no significant differences in insulin sensitivity between the two groups. In comparison to the islets in control mice, the islets in the uric acid–treated mice were markedly smaller in size and contained less insulin. Treatment of β-cells in vitro with uric acid activated the NF-κB signaling pathway through IκBα phosphorylation, resulting in upregulated inducible nitric oxide synthase (iNOS) expression and excessive nitric oxide (NO) production. Uric acid treatment also increased apoptosis and downregulated Bcl-2 expression in Min6 cells. In addition, a reduction in insulin secretion under glucose challenge was observed in the uric acid–treated mouse islets. These deleterious effects of uric acid on pancreatic β-cells were attenuated by benzbromarone, an inhibitor of uric acid transporters, NOS inhibitor L-NMMA, and Bay 11–7082, an NF-κB inhibitor. Further investigation indicated that uric acid suppressed levels of MafA protein through enhancing its degradation. Collectively, our data suggested that an elevated level of uric acid causes β-cell injury via the NF-κB-iNOS-NO signaling axis.
Extensive research over the last 10 years has provided evidence of the anti-cancer activities of GLTs in different stages of carcinogenesis. These activities include cell cycle arrest, induction of apoptosis and autophagy, and suppression of metastasis and angiogenesis. However, the exact molecular mechanisms involved in these processes remain unclear. Androgen receptor, nuclear factor-kappa B, activator protein-1, p53 and 14-3-3 are reportedly involved in the anti-cancer properties of GLTs. Animal models further shed light on the development of GLTs as anti-cancer agents. However, more research and clinical trials are necessary to exploit these compounds.
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