Shikonin

At nanomolar concentrations, shikonin inhibits monocyte chemotaxis and calcium flux in response to a variety of CC chemokines (CCL2 [monocyte chemoattractant protein 1], CCL3 [macrophage inflammatory protein 1α], and CCL5 [regulated upon activation, normal T-cell expressed and secreted protein]), the CXC chemokine (CXCL12 [stromal cell-derived factor 1α]), and classic chemoattractants (formylmethionyl-leucine-phenylalanine and complement fraction C5a). Shikonin down-regulates surface expression of CCR5, a primary HIV-1 coreceptor, on macrophages. The anti-HIV and anti-inflammatory activities of shikonin may be related to its interference with chemokine receptor expression and function^[1]. Shikonin inhibits enterocyte calcium-activated chloride channels, the inhibitory effect is partially through inhibition of basolateral K+ channel activity^[2].

Freshly isolated human monocytes are plated in a 96-microwell plate (Costar) at 10⁵ cells per well with shikonin at a final concentration of 10, 1, 0.1, 0.01 μM. The numbers of viable cells, as detected by MTS test and the trypan blue exclusion assay, were measured 12 and 24 h after incubation at 37°C in humidified air with 5% CO2.

Shikonin significantly delays intestinal motility in mice and reduces stool water content in a neonatal mice model of rotaviral diarrhea without affecting the viral infection process in vivo. Shikonin has been reported to have antioxidant, antibacterial, antiparasitic, antiviral and wound-healing activities. Shikonin inhibits allergic action as well as tracheal hyperresponsiveness in vivo. Intraperitonal injection of shikonin has been demonstrated to result in some toxicity, with an LD50 of 20 mg/kg. Shikonin absorption is fast if given by oral gavage and muscle injection, as it is barely detected in the plasma after 1 min, with a oral gavage yielding a bioavailability of about 34%^[2].