Medium composition and methyl jasmonate influence the amount and spectrum of secondary metabolites in callus cultures of Zanthoxylum stenophyllum Hemsl.

In the present study callus cultures of Zanthoxylum stenophyllum were initiated in vitro and the effect of different growth regulators and elicitors was tested both upon callus growth and secondary metabolite production. On a medium containing naphthalenacetic acid (NAA), kinetin and 2,4 dichlorophenoxyacetic acid (2,4D), a yellowish and friable callus was obtained from 90% of cotyledon explants, while no callus appeared from other portions of the seedlings. The time course of callus growth and secondary metabolite accumulation was followed after subculturing the established callus culture on different media containing various hormonal combinations. Results indicate that medium containing NAA and a higher concentration of 2,4-D compared to maintenance medium gave the highest stimulation of callus growth, suggesting that this auxin has a critical role in influencing growth. Addition of an organic nitrogen source such as casein hydrolysate also had a positive effect on growth. HPLC analysis of methanol extractable secondary metabolites from Z. stenophyllum calli grown on different media showed that phytohormones and nutrients were able to modify the chromatographic pattern of compounds. Calli grown on the medium giving the highest stimulation of growth show a reduced accumulation of some secondary products. Under the same hormonal conditions, the presence or absence of casein also altered the metabolites produced, both qualitatively and quantitatively. In response to elicitation by methyl jasmonate (MJ), metabolite production was different for the different classes of compounds, and hormonal composition of the culture medium turned out to be very important in determining the response to MJ. Thus, results confirm the importance of the reciprocal interactions between hormones, nutrients and elicitors when attemps are made to enhance secondary metabolite accumulation in in vitro cultures

Irbic acid, a dicaffeoylquinic acid derivative from Centella asiatica cell cultures

3,5-O-dicaffeoyl-4-O-malonilquinic acid (1) (irbic acid) has been isolated for the first time from cell cultures of Centella asiatica and till now it has never been reported to be present in the intact plant. Evidence of its structure was obtained by spectroscopic analyses (MS/NMR). Besides 1, cell cultures produce also the known 3,5-O-dicaffeoylquinic acid, chlorogenic acid, and the triferulic acid 2 (4-O-8′/4′-O-8″-didehydrotriferulic acid). Biological activities were evaluated for compound 1, which showed to have a strong radical scavenging capacity, together with a high inhibitory activity on collagenase. This suggests a possible utilization of this substance as a topical agent to reduce the skin ageing process