Melanogenesis inhibitory pregnane glycosides from Cynanchum atratum

Anti-Melanogenic Effects of Fractioned Cynanchum atratum by Regulation of cAMP/MITF Pathway in a UVB-Stimulated Mice Model

Based on traditional pharmacological applications and partial in vitro data, Cynanchum atratum (CA) is proposed to act on skin whitening. However, its functional evaluation and underlying mechanisms have yet to be identified. This study aimed to examine the anti-melanogenesis activity of CA fraction B (CAFB) on UVB-induced skin hyperpigmentation. Forty C57BL/6j mice were exposed to UVB (100 mJ/cm², five times/week) for eight weeks. After irradiation, CAFB was applied to the left ear once a day for 8 weeks (the right ear served as an internal control). The results showed that CAFB significantly reduced melanin production in the ear skin, as indicated by the gray value and Mexameter melanin index. In addition, CAFB treatment notably decreased melanin production in α-MSH-stimulated B16F10 melanocytes, along with a significant reduction in tyrosinase activity. Cellular cAMP (cyclic adenosine monophosphate), MITF (microphthalmia-associated transcription factor), and tyrosinase-related protein 1 (TRP1) were also noticeably downregulated by CAFB. In conclusion, CAFB is a promising ingredient for treating skin disorders caused by the overproduction of melanin and its underlying mechanisms involving the modulation of tyrosinase, mainly mediated by the regulation of the cAMP cascade and MITF pathway.

A review of the ethnopharmacology, phytochemistry and pharmacology of Cynanchumatratum

ETHNOPHARMACOLOGICAL RELEVANCE

The dried roots and rhizomes of Cynanchum atratum Bunge is named 'Baiwei' according to traditional Chinese medicine theory. It is also named Cynanchi atrati Radix in Chinese Pharmacopoeia. Cynanchi atrati Radix is famous for its medicinal value of clearing away heat, relieving drenching, detoxifying and treating abscesses. It was commonly used in some Asian countries for the treatment of fever, vasoconstrictive syncope, lymphangitis and other diseases, obviously due to the effect of C₂₁ steroidal glycosides.

THE AIM OF THE REVIEW

The review concentrates on the botany, ethnopharmacology, phytochemistry, pharmacology and toxicology of Cynanchum atratum. We also discuss expectations for prospective research and implementation of this herb.

MATERIALS AND METHODS

Relevant information about C. atratum was gained from ancient books and records, Doctoral and master's Theses, Science Direct, Pubmed, Wiley, CNKI, WanFang DATA, Google Scholar and other domestic and foreign literature. Some electronic databases have been included.

RESULTS

As a member of the Apocynaceae family, C. atratum possesses its up-and-coming biological characteristics. It is widely reported for treating of postpartum fatigue, vomiting, urine drops, nephritis, urinary tract infection, edema, bronchitis and rheumatic low back pain. By now, over 100 compounds have been identified from C. atratum, including C₂₁ steroidal glycosides, acetophenones, alkaloids, volatile oil and other ingredients. Activities such as anti-inflammatory, anti-tumor, anti-virus, antibacterial, anti-forgetful and others have been corroborated in vivo and in vitro. In addition, many of the active ingredients, such as Cynatratoside A, Cynanversicoside A, B, D, G, p-hydroxyacetophenone, 2,4-dihydroxyacetophenone and some volatile oils have been used as quality markers.

CONCLUSION

All kinds of research conducted on C.atratum, especially in field of ethnopharmacological use, phytochemicals and pharmacology have been reviewed. The herb has been used over the years in treating nephritis, urinary tract infection, bronchitis and rheumatic lumbocrural pain. Many studies have been carried out to identify compounds that play a leading role in drug activity. However, the mechanism of drug therapy remains unclear. The evidence used to prove the quality standard of medicinal materials is obviously inadequate. Besides, safety evaluation is necessary for clinical medication. Similarly, the separation of steroidal saponins and the development of new drugs will also need further discussion.

Cynanchum atratum Alleviates Non-Alcoholic Fatty Liver by Balancing Lipogenesis and Fatty Acid Oxidation in a High-Fat, High-Fructose Diet Mice Model

Cynanchum atratum, a medicinal herb, is traditionally used as an antidote, diuretic, and antipyretic in eastern Asia. The current study aimed to investigate the anti-fatty liver capacity of the ethanol extract of Cynanchum atratum (CAE) using a 10-week high-fat, high-fructose diet mouse model. A six-week treatment of CAE (from the fifth week) significantly attenuated the weights of the body, liver, and mesenteric fat without a change in diet intake. CAE also considerably restored the alterations of serum aminotransferases and free fatty acid, fasting blood glucose, serum and hepatic triglyceride, and total cholesterol, as well as platelet and leukocyte counts. Meanwhile, CAE ameliorated hepatic injury and lipid accumulation, as evidenced by histopathological and immunofluorescence observations. Additionally, CAE significantly lowered the elevation of hepatic TNF-α, the TNF-α/IL-10 ratio, fecal endotoxins, and the abundance of Gram-negative bacteria. Hepatic lipogenesis and β-oxidation-related proteins and gene expression, including PPAR-α, SREBP-1, SIRT1, FAS, CTP1, etc., were normalized markedly by CAE. In particular, the AMPK, a central regulator of energy metabolism, was phosphorylated by CAE at an even higher rate than metformin. Overall, CAE exerts anti-hepatic steatosis effects by reducing lipogenesis and enhancing fatty acid oxidation. Consequently, Cynanchum atratum is expected to be a promising candidate for treating chronic metabolic diseases.

A C21-Steroidal Glycoside from Cynanchum atratum Attenuates Concanavalin A-Induced Liver Injury in Mice

Cynatratoside A (CyA) is a C₂₁ Steroidal glycoside with pregnane skeleton isolated from the root of Cynanchum atratum Bunge (Asclepiadaceae). This study aimed to investigate the effects of CyA on concanavalin A (Con A)-induced autoimmune hepatitis (AIH) and the underlying mechanism. CyA was orally administered to mice at 10 and 40 mg/kg 8 h before and 1 h after Con A treatment. The effects of CyA on Con A-induced spleen and liver in mice were assessed via histopathological changes, T lymphocyte amounts and the expressions of IL-1β and ICAM-1. Con A-induced L-02 hepatocytes were used to evaluate whether CyA (0.1–10 μM) can directly protect hepatocytes from cytotoxicity and the possible mechanism. The results revealed that CyA treatment could significantly improve the histopathological changes of spleen and liver, reduce the proliferation of splenic T lymphocytes, and decrease the expressions of IL-1β and ICAM-1 in liver. The experiment in vitro showed that CyA inhibited Con A-induced hepatotoxicity in a concentration-dependent manner. CyA (10 μM) significantly increased/decreased the expression of Bcl-2/Bax and reduced the levels of cleaved caspases-9 and -3. Our study demonstrated for the first time that CyA has a significant protective effect on Con A-induced AIH by inhibiting the activation and adhesion of T lymphocytes and blocking hepatocyte apoptosis.

Inhibitory Effect of 7-Demethoxytylophorine on Penicillium italicum and its Possible Mechanism

7-demethoxytylophorine (DEM) is a phenanthroindolizidine alkaloid, which is reported to be effective in inhibiting leucocytes and regulation of human immunity. However, few studies reported the inhibitory effect of DEM against plant-pathogenic fungi, particularly postharvest pathogen Penicillium italicum (P. italicum). Current studies have investigated the antifungal activity of DEM through membrane damage and energy deficit in P. italicum. The results showed that the DEM potentially inhibits the growth of P. italicum in a dose-dependent manner. In vitro (mycelial growth and spore germination) tests showed great minimal inhibitory concentration (MIC) (1.56 µg mL-1) and minimum fugicide concentration (MFC) (6.25 µg mL-1). Microscopic analyses showed that mycelial morphology of P. italicum was severely damaged following DEM treatment. Moreover, relative electrical conductivity and lysis ability assays showed that DEM treatment aids in destroying the integrity of plasma membranes that deplete reducing sugars and soluble proteins. The activity of malate dehydrogenase (MDH) and succinate dehydrogenase (SDH) demonstrated that DEM led to the disruption of TCA cycle in P. italicum mycelia. The results of this study led us to conclude that, DEM could be used as a natural antifungal agent for controlling postharvest blue mold disease of citrus fruits caused by P. italicum.