Effects of antiinflammatory triterpenes isolated from Leptadenia hastata latex on keratinocyte proliferation.

Several triterpenes isolated from Leptadenia hastata latex were tested for their anti-inflammatory activity. Lupeol (1), its acetate (2) and palmitate (3) esters were found to be the main antiinflammatory constituents in the croton oil-induced ear oedema test. Furthermore, lupeol hemisuccinate (4), synthesized from lupeol, exhibited a higher activity than lupeol in the test. These results prove that the triterpenes play a pivotal role in the topical antiinflammatory effect of this latex. In addition, an in vitro model of human skin keratinocytes (epidermal explants) cultured at an air-liquid interface on a de-epidermized human dermis (DED) was used to investigate the effects of lupeol esters on skin repair in vitro. Compared with the control, compounds 2 and 3 improved keratinocyte proliferation at a concentration of 5 microM in the culture medium; however, they remained less active than compounds 1 and 4. In contrast to compound 1, all the lupeol esters (2-4), and particularly compound 4, induced a good differentiation of keratinocytes with a well-formed stratum corneum without parakeratosis. These results substantiate the topical use of Leptadenia hastata latex in traditional medicine and showed that both antiinflammatory activity and the effect on keratinocyte proliferation of compound 1 could be improved by its hemisuccinylation; on the contrary, esterification by acetylation or palmitoylation decreased these activities.