Phytomedicine may Lead to New Drugs for psoriasis

Psoriasis is a chronic relapsing skin condition that affects approximately 125 million people worldwide. The typical features of psoriasis include significant thick, red, well-defined patches of skin with flaky and silver-white scales. Stress, infections from bacteria or viruses, skin injury, and immune system abnormalities can promote the development of psoriasis.

Cajanus cajan (L.) Millsp.(“C.cajan”for short hereinafter), also known as pigeon pea, is an important food and forage crop in Egypt, Africa, and Asia. In ancient times, the extraction of juice from C.cajan leaves was employed for the treatment of inflammations and various skin conditions. This historical practice serves as fundamental evidence that underscores the potential of C.cajan leaves in the development of skin care.

In a new study published on November 14 in Journal of Ethnopharmacology, a research group led by Professor QIU Shengxiang of South China Botanical Garden (SCBG), Chinese Academy of Sciences, has made great progress in investigating the potential therapeutic effects and underlying molecular mechanisms of stilbene-enriched extracts from the leaves of C.cajan as a functional drug for psoriasis. This study is titled "Stilbene-enriched extract from the leaves of C.cajan attenuates psoriasis in imiquimod-induced psoriatic mice by targeting aryl hydrocarbon receptor and chemokines". Dr. ZHU Baojun and Dr. YAO Liyuan are the co-first authors, while assistant researcher Dr. ZHAO Liyun and professor QIU Shengxiang are the co-corresponding authors.

The stilbene-enriched active components including cajaninstilbene, longistylin A, and longistylin C, were extracted from the ethyl acetate (EtOAc) extract enriched with stilbenes from C.cajan leaves (“EXT” for short hereinafter). The researchers found that EXT demonstrated efficacy in alleviating the symptoms of IMQ-induced psoriasis in a mouse model. By making use of transcriptomic and proteomic analysis, the research team found significant downregulation of numerous chemokines (Ccl2, Ccl20, and Cxc5, etc.), pro-inflammatory cytokines (Il17a, Il19, Il22, and Il23, etc.), and genes associated with keratinocyte differentiation (Lce and Sprr family genes).

Researchers conclude that the aryl hydrocarbon receptor (AhR) and genes of the cytochrome P450 family are activated by EXT. This study is the first to demonstrate that the ethyl acetate (EtOAc) extract enriched with stilbenes from EXT effectively alleviates symptoms in IMQ-induced psoriatic mice. The mechanism involves the activation of the AhR and a subsequent reduction in the production of various inflammatory chemokines and cytokines. These findings suggest that EXT holds significant potential as a plant-derived therapeutic agent for the treatment of psoriasis.

The article link is: https://doi.org/10.1016/j.jep.2024.119109

Fig.1. Photo of C.cajan leaves and LC-MS-based phytochemical fingerprint of EXT spectrum with stilbenes highlighted (Image by YAO et al)

Fig.2. The effect and hypothetical mechanism of EXT in the treatment of psoriasis (Image by YAO et al)