Identification of oxidative products of pterostilbene and 3'-hydroxypterostilbene in vitro and evaluation of anti-inflammatory and anti-cancer cell proliferative activity

Pterostilbene (trans-3,5-dimethoxy-4ʹ-hydroxystilbene) is an important phenolic compound which is reported as a potential anti-oxidative, anti-inflammatory, and anti-cancer agent. It is a natural compound and belongs to the group of phytoalexins, agents produced by plants to fight infections like chemicals and fungal. In nature, pterostilbene can be oxidized by peroxidase from fungus, and peroxidase also exists in human body. So it may undergo oxidative process in human as well. 3ʹ-hydroxypterostilbene is another natural phenolic compound and also is a metabolite of pterostilbene identified in mouse. The two adjacent hydroxyl groups in its molecule indicate that it may have a stronger bioactivity than pterostilbene. To understand the possible oxidative reaction and major products in metabolic process, this research use peroxidase and phosphate-citrate buffer to simulate the peroxidation of pterostilbene and 3ʹ-hydroxypterostilbene in vitro. The major oxidative products were identified as pterostilbene trans dehydrodimer and 3ʹ-hydroxypterostilbene trans dehydrodimer by LC/MS and NMR. The anti-inflammatory and anti-cancer cell proliferative activity of three compounds, pterostilbene, 3ʹ-hydroxypterostilbene, and pterostilbene trans dehydrodimer, was evaluated in this research. In anti-inflammatory evaluation, Griess assay was used to measure the nitric oxide production in RAW264.& cells which were treated with the three compounds at different concentration. In anti-cancer cell proliferative study, MTT assay was used to measure the cell viability of two cancer cell lines: drug-sensitive HL-60 leukemia cell line and drug-resistant MDA-MB231 breast cancer cell line. According to our data, 3ʹ-hydroxypterostilbene had a significant anti-inflammatory and anti-cancer cell proliferative activity.