Isolation and structure determination of phytochemicals from senna dydimobotrya leaf extract used in cancer management

Abstract

Cancer is the second leading cause of death worldwide accounting for an estimated 10 million cancer deaths by 2020 with more deaths recorded in economically developing countries. Cancer cases are projected to double by 2030 globally with more cases expected in resource constrained countries particularly in Africa and Asia. Available cancer treatment options such as chemotherapy, radiotherapy, and surgery have several untolerable side effects in addition to high cost associated with them making it difficult for cancer management especially in resource constrained settings. Due to these challenges, a big number of people have resorted to the use of medicinal plants as alternative therapies because they are thought to be effective, safe and easily accessible. Senna didymobotrya is a flowering plant in the family caesalpiniaceae which has been exploited in traditional medicine for management of different diseases including cancer. In some communities in Uganda for example, leaves of S. dydimobotrya have been reported to be used traditionally for cancer management. However, the phytochemical compounds responsible for this therapeutic property are not known. This study aimed at carrying out extraction, evaluating the antiproliferative potential of the leaf extract and to isolate the compounds from S. didymobotrya. First, the leaf extract was tested against two cancer cell lines, A549 lung adenocarcinoma cell line and NCI-H441 Non-Small Cell Lung Carcinoma Tissue to determine antiproliferative activity. Next the leaf extract was assayed using Ultra high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) and the spectra were subjected to deriplication analysis on the global natural products social molecular networking (GNPS) library. This yielded 26 compounds which include Quercetin-4'-O-glucoside, Calycosin-7-O-beta-D-glucoside, GalCer, Sarmentoside B, Pseudobaptigenin, 3,3',4'-Trimethoxyflavone among others. Furthermore, the extracts were subjected to chromatographic isolation and the structures of the isolated compounds were determined by analysis of 1D and 2D NMR and Mass spectra. Three compounds Rutin, Chrysophanol and physcion were isolated from the methanol extract. Rutin shows significant antiproliferative activity with an IC50 value of 100µg/ml and this justifies the use of this plant for cancer management in local communities.