Studies on tissue cultures of the genus Cinchona L. alkaloid production in cell suspension cultures

Phylogeny Predicts the Quantity of Antimalarial Alkaloids within the Iconic Yellow Cinchona Bark (Rubiaceae: Cinchona calisaya)

Considerable inter- and intraspecific variation with respect to the quantity and composition of plant natural products exists. The processes that drive this variation remain largely unknown. Understanding which factors determine chemical diversity has the potential to shed light on plant defenses against herbivores and diseases and accelerate drug discovery. For centuries, Cinchona alkaloids were the primary treatment of malaria. Using Cinchona calisaya as a model, we generated genetic profiles of leaf samples from four plastid (trnL-F, matK, rps16, and ndhF) and one nuclear (ITS) DNA regions from twenty-two C. calisaya stands sampled in the Yungas region of Bolivia. Climatic and soil parameters were characterized and bark samples were analyzed for content of the four major alkaloids using HPLC-UV to explore the utility of evolutionary history (phylogeny) in determining variation within species of these compounds under natural conditions. A significant phylogenetic signal was found for the content of two out of four major Cinchona alkaloids (quinine and cinchonidine) and their total content. Climatic parameters, primarily driven by changing altitude, predicted 20.2% of the overall alkaloid variation, and geographical separation accounted for a further 9.7%. A clade of high alkaloid producing trees was identified that spanned a narrow range of altitudes, from 1,100 to 1,350 m. However, climate expressed by altitude was not a significant driver when accounting for phylogeny, suggesting that the chemical diversity is primarily driven by phylogeny. Comparisons of the relative effects of both environmental and genetic variability in determining plant chemical diversity have scarcely been performed at the genotypic level. In this study we demonstrate there is an essential need to do so if the extensive genotypic variation in plant biochemistry is to be fully understood.

In vitro manipulation and propagation of medicinal plants

Well developed techniques are currently available to help growers meet the demand of the pharmaceutical industry in the next century. These protocols are designed to provide optimal levels of carbohydrates, organic compounds (vitamins), mineral nutrients, environmental factors (e.g. light, gaseous environment, temperature, and humidity) and growth regulators required to obtain high regeneration rates of many plant species in vitro and thereby facilitate commercially viable micropropagation. Well-defined cell culture methods have also been developed for the production of several important secondary products. An overview of the regeneration of medicinal plants by direct and indirect organogenesis and by somatic embryogenesis from various types of explants is presented, and the use of these techniques combined with other biotechnological approaches to improve medicinal plants through somaclonal variation and genetic transformation is reviewed.

In vitro cultures of Cinchona species : Precursor feeding of C. ledgeriana root organ suspension cultures with L-Tryptophan

The uptake of L-[methylene-(14)C]-tryptophan from culture medium into root organs of Cinchona ledgeriana and the subsequent incorporation of the radiolabel into quinine and quinidine is reported. In addition, feeding unlabelled L-tryptophan at levels of 500mg/l to the cultures results in a 5-fold increase in the yields of both quinoline alkaloids.

Shikimate pathway activity in shake and fermenter cultures of Cinchona succirubra

Cell suspension cultures of Cinchona succirubra were cultivated in shake cultures and for the first time in airlift fermenters. Under both conditions L-tryptophan exerts a stimulatory effect on alkaloid formation. In this context the regulatory pattern of some shikimate pathway enzymes was investigated in non-supplemented and tryptophan supplemented Cinchona cell cultures. A remarkable increase of tryptophan decarboxylase (TDC) activity was observed in Cinchona cells under the influence of tryptophan. Apparently, like in some other indole alkaloid producing cell cultures, a high TDC activity is a prerequisite for alkaloid formation. Growth pattern and some enzyme activities of C. succirubra fermenter cultures at controlled and non-regulated pH levels were followed. Optimum growth and alkaloid formation were recorded under non-regulated (normal) pH conditions.