2016_05: Citrus Treasures

What is the topic?

In South China there is a great diversity of Citrus-species and there these fruits were domesticated the first time. In addition to the species and varieties known to us, there are many, not known in Europe, but used since ancient times in Traditional Chinese Medicine. Together with our "alumna" Dr. Xin Guan and the Chinese Citrus expert Dr. Zhou at the Southwest University in Chongqing we try to uncover those hidden treasures. For this purpose, we compared different Citrus extracts from species that are active against tumours with those that lacked such an activity.

What was found?

Using fluorescently labelled microtubules we tested, if and how these extracts act upon microtubules - most compounds currently used for the chemotherapy of cancer, such as Paclitaxel from the Pacific Yew, attack the microtubules of the rapidly dividing cancer cells. In fact, we could observe in the extracts of active species an effect on microtubules, whereby the effect was specific and dependent on the species. One type of extracts produced short microtubules indicating that the integration of tubulin into the growing end was impaired, whereas a second type of extract had the opposite effect. Also for the nucleation of new microtubules we could find positively and negatively acting extracts.

What to do with these results?

The active extracts will now be separated further and their secondary metabolites will be identified. The comparison of compound profile and microtubule effect allows to define first "hot candidates". These can then be investigated more closely and their mode of action can be determined. For one compound from this approach, gallic acid, we have done this already with success (more on Gallic Acid) - here, we showed a mechanism that only affects the division spindle of cancer cells, not that of healthy cells. Now, we hope to find additional interesting molecules.

Publication

125. Guan X, Tan S, Zhou Z, Buchholz G, Nick P (2016) A method to evaluate the bioactive function of fruit extracts of Chinese wild Citrus with microtubular activity. J Integr Agriculture 16, 867-873 - pdf