Potential cancer chemopreventive activity of some goji berry pyrrole alkaloids isolated from a mislabeled commercial sample

Goji berry [fruit of Lycium barbarum L. (Solanaceae)] has a long history of usage in Asian countries as a culinary ingredient, traditional medicine and functional food. Goji has more recently become increasingly popular in Europe and North America as a “super fruit” and botanical dietary supplement. One commercial dietary supplement that was screened in an ongoing search for natural inhibitors of carcinogenesis showed hydroxyl radical-scavenging (HRS) and quinone reductase-inducing (QRI) activities. This sample was shown by chemotaxonomy and microscopy to be mislabeled, and was identified as Goji. Isolation directed by the above bioassays yielded a new pyrrole alkaloid (1) along with seven known compounds (2 – 8). Compound 1 demonstrated HRS activity with an ED₅₀ value of 16.7 µM, and compound 2 was active in both HRS (ED₅₀ 11.9 µM) and QRI [CD (concentration required to double quinone reductase activity) 2.4 µM)] assays. Further investigation confirmed the presence of compounds 1 – 2 and 4 – 8 in a Goji extract that was previously shown to prevent N-nitrosomethylbenzylamine-induced esophageal cancer in rats. Taken together with the dietary source of these molecules having a long history of human consumption, the results of the study indicated that this class of compounds, especially compound 2, could be potential in vivo cancer chemopreventive agents.