Orthosiphon aristatus (Bl.) Miq. (syn. Orthosiphon grandiflorus Bold, syn. Orthosiphon spicatus (Thunb.) Bak., syn. Orthosiphon stamineus Benth.) is a member of the Lamiaceae () native to tropical Asia and is currently under cultivation in Indonesia, the main exporter of this medicinal plant (). Due to its broad distribution as a medicinal plant, 0. aristatus has adopted several synonymes such as Indischer Nierentee (German), Koemis koetjihg (Dutch), Kumis kuting (Indonesian), Java tea (English) or feuilles de barbiflore (French) (). Leaves of Orthosiphon aristatus (Orthosiphonis folium DAB 10) are used to prepare a tea which is known for its diuretic properties. The tea is especially recommended as a treatment of chronic kidney or bladder inflammations (). In addition to its diuretic effect, the tea is reported to cause increased excretion of NaCl (). The bioactive constituents of this medicinal plant, however, are still basically unknown.
In a previous study with differentiated plants of Orthosiphon aristatus we showed for the first time that hydroxycinnamic acid derivatives such as the main compound rosmarinic acid () are the major phenolic constituents present in leaves and stems (). The predominance of rosmarinic acid in this herbal drug is of interest, since this depside is known to be pharmacologically active. Rosmarinic acid is a natural antioxidant () and is probably involved in the virussatic properties of extracts derived from Melissa spp. (). Rosmarinic acid has also antigonadotropic activity (). We have now analyzed cell suspension cultures of Orthosiphon aristatus with regard to phenolic secondary compounds and report on the elicitation of rosmarinic acid production following addition of yeast extract to the liquid growth media.
Yeast extract has been shown to be an effective elicitor, capable of inducing a significantly enhanced accumulation of RA as well as of a biogenetically related phenolic compound in cell suspension cultures of Orthosiphon aristatus. This induction of RA accumulation is due to de novo biosynthesis as demonstrated by feeding studies employing 14C-labelled precursors as well as by enzyme studies. Bioassay guided fractionation of the yeast extract resulted in the isolation of two bioactive fractions (elicitor A and B). Both elicitors were polysaccharides consisting mainly of mannose, glucose, and galactose moieties but differed from each other with regard to the relative proportions of the respective sugars and with regard to their molecular weights. Elicitors A and B differ from a previously described glucan elicitor isolated from yeast extract () both with regard to their carbohydrate composition and with regard to the linking patterns of the sugars. Glucomannan elicitors, however, had previously been isolated from cell walls of the fungus Phytophthora megasperma and were reported to be more active than co-occurring glucan elicitors with regard to the induction of glyceollin accumulation in soybean (Glycine max) (). The Mr of the most active glucomannan elicitor from P. megasperma was ca. 40000, the relative proportions of mannose and glucose following hydrolysis were 11:9. The Mr of the elicitor from P. megasperma is thus twice as high as that of elicitor A from yeast extract isolated in this study, whereas the composition and the relative proportions of the sugars from elicitor A and B and the glucomannan from P. megasperma are similar and thus seem to be chemically related.
Selections from the book: “Medicinal and Aromatic Plants V”, 1993.