Anti-inflammatory action has been demonstrated for anthraquinones produced from rhubarb.

A new study published in Biomedicine and Pharmacotherapy sought to evaluate the topical administration of rhubarb anthraquinone aglycones for the treatment of psoriasis. To establish a structure-permeation link, antipsoriatic impacts of five anthraquinones, including aloe-emodin, rhein, emodin, physcion and chrysophanol, were assessed. Physicochemical parameters were determined using molecular modeling. In the cell-based study, both macrophages (differentiated THP-1) and keratinocytes (HaCaT) were employed to assess anti-inflammatory efficacy.

In vitro pig skin absorption revealed that chrysophanol had the largest cutaneous accumulation. Rhein was found to be mainly transported to the receptor compartment when administered topically. Compared to intact skin, rhein absorption was increased by a factor of five in barrier-deficient skin. The anthraquinones dramatically lowered IL-6, IL-23, and TNF when macrophages were stimulated with imiquimod (IMQ) to imitate the inflammation in psoriasis. The amount of cytokine inhibition was equivalent across the five drugs. By suppressing the activation of MAPK and NF-B signaling, anthraquinones reduced cytokines. Anthraquinones also reduced the levels of IL-6, IL-8 and IL-24 in TNF-stimulated inflammatory keratinocytes. Rhein and chrysophanol were both effective in inhibiting STAT3 phosphorylation in keratinocytes generated by stimulated macrophage conditioned media. Topically administered rhein or chrysophanol improved scaling, erythema and epidermal hyperplasia in the IMQ-induced psoriasiform mouse model. Meanwhile, the IMQ-induced epidermal acanthosis was reduced three-fold with rhein and chrysophanol. Both, anthraquinone compounds reduced the number of macrophages and neutrophils in the skin lesion, skin-draining lymph node and spleen, according to histological profiles.

It was concluded that Rhein and chrysophanol demonstrates multifunctional inhibition by modulating multiple sites for psoriasiform inflammation relief.

Source: Biomedicine & Pharmacotherapy. 2022 Jan;145:112482. doi: 10.1016/j.biopha.2021.112482.