Lippia dulcis Trevis. an Aztecan sweet herb of potential interest

The demand for new alternative sweeteners for diabetic purposes has increased worldwide [1]. Recent research for the discovery and evaluation of potentially non-cariogenic sweeteners from plants has focused on plant derived compounds of terpenoid types like in our herb [2]. Lippia dulcis is a Verbenaceae native to tropical America and contains sesquiterpenoid sweeteners in the essential oil like (+)-hernandulcin and (+)-4β-hydroxyhernandulcin [3,4]. We have isolated the essential oils from two populations of this species, originated from Mexico and Panama, by steam distillation and analyzed them with the gas chromatography. The oil of the Mexican plants contains about 30% camphor and about 10% hernandulcin, whereas the oil of the Panamic plants contains about 17% hernandulcin and only traces of camphor <0,015%. Sweetness estimation of hernandulcin which was purified by column chromatography showed that it may be app. 500 times sweeter than sucrose. The cytotoxicity of ethanolic extract of the Mexican plants, camphor, hernandulcin, and the two types of essential oils were assessed in HepG2 cells by measuring the reduction of the MTT [5] and IC₅₀ values were determined. The essential oils and hernanadulcin showed mild toxicity on HepG2- cells [IC₅₀ app. 150µg/ml (oil of Mexico), 70µg/ml (oil of Panama), and 68µg/ml, respectively]. However, the ethanolic extract and the component camphor showed no effect on these cells at concentrations up to 250µg/ml.

References: [1] Kim, NC. et al. (2002) Arch Pharm Res. 25: 725–746. [2] Kinghorn, AD. et al. (2002) Pure Appl. Chem. 74: 1169–1179. [3] Kaneda, N. et al. (1992) J. Nat. Prod. 55: 1136–1141. [4] Compadre, CM. et al. (1985) Science 227: 417–419. [5] Mosmann, T. (1983) J. Immunol. Methods 65: 55–63.