4H-1-benzopyran-4-ones (chromones) are important naturally-distributing compounds. As compared with flavones, isoflavones and 2-styrylchromones, there are only few papers of 3-styrylchromones that have been published. We have previously reported that among fifteen 3-styrylchromone derivatives, three new synthetic compounds that have OCH3 group at the C-6 position of chromone ring, (E)-3-(4-hydroxystyryl)-6-methoxy-4H-chromen-4-one (compound 11), (E)-6-methoxy-3-(4-methoxystyryl)-4H-chromen-4-one (compound 4), (E)-6-methoxy-3-(3,4,5-trimethoxystyryl)-4H-chromen-4-one (compound 6) showed much higher cytotoxicities against four epithelial human oral squamous cell carcinoma (OSCC) lines than human normal oral mesenchymal cells. In order to further confirm the tumor specificities of these compounds, we compared their cytotoxicities against both human epithelial malignant and non-malignant cells, and then investigated their effects on fine cell structures and metabolic profiles and cell death in human OSCC cell line HSC-2. Cytotoxicities of compounds 4, 6, 11 were assayed with MTT method. Fine cell structures were observed under transmission electron microscope. Cellular metabolites were extracted with methanol and subjected to CE-TOFMS analysis. Compounds 4, 6, 11 showed much weaker cytotoxicity against human oral keratinocyte and primary human gingival epithelial cells, as compared with HSC-2, confirming their tumor-specificity, whereas doxorubicin and 5-FU were highly cytotoxic to these normal epithelial cells, giving unexpectedly lower tumor-specificity. The most cytotoxic compound 11, induced the mitochondrial vacuolization, autophagy suppression followed by apoptosis induction, and changes in the metabolites involved in amino acid and glycerophospholipid metabolisms. Chemical modification of lead compound 11 may be a potential choice for designing new type of anticancer drugs.

Background/Aim: Studies of biological activity of 2styrylchromone derivatives focusing on antioxidant, antiinflammatory, antiviral and antitumor activity are limited. In this study, eighteen synthetic 2-styrylchromone derivatives were investigated for their cytotoxicity against human malignant and non-malignant cells, and then subjected to quantitative structure-activity relationship (QSAR) analysis. Materials and Methods: Tumor-specificity was calculated by the ratio of mean 50% cytotoxic concentration (CC 50) against four normal oral cells to that against oral squamous cell carcinoma cell lines. Induction of apoptosis and growth arrest were evaluated by cellcycle analysis. For QSAR analysis, 3,117 types of physicochemical, structural, and quantum chemical features were calculated from the most stabilized structure of 2styrylchromone derivatives. Results: Two 2-styrylchromone derivatives in which a methoxy group was introduced at the 4position of the benzene ring showed tumor-specificity equivalent to or higher than doxorubicin in TS value. These compounds accumulated the subG 1 and G 2 /M phase cells, suggesting the induction of apoptosis. Their tumor-specificity can be explained mainly by molecular shape and electronic state. Conclusion: These findings suggest the applicability of 2-styrylchromone to develop safe and effective anticancer agents as seed compounds. Our group recently found that low-molecular weight natural polyphenols, such as tannins and flavonoids showed very low anticancer activity (evaluated by tumor-specificity with human cultured malignant and none-malignant cells) (1). On the other hand, chemical modification of chromone, two ring backbone structure present in flavonoids, yielded derivatives with much higher tumor-specificity (2, 3). 2-Styrylchromone is a derivative having a styryl group bonded to the 2-position of the chromone skeleton. Synthetic 2styrylchromone derivatives have been reported to show radical scavenging (4, 5), anti-inflammatory (6), hepatoprotective (7), neuroprotective (8-10), anti-human immunodeficiency virus (11), anti-norovirus (12), anti-rhinovirus (13, 14), antitumor (15-18), and monoamine oxidase B inhibiting (19) activity. However, very few studies tested their cytotoxicity against normal cells (16). In the present study, we investigated the cytotoxicity of eighteen synthetic 2-styrylchromone derivatives (Figure 1) against four human oral squamous cell carcinoma (OSCC) cells lines (Ca9-22, HSC-2, HSC-3, HSC-4) and three human normal oral mesenchymal cells [human gingival fibroblast (HGF), human periodontal ligamental fibroblast (HPLF) and human pulp cell (HPC)], and performed quantitative structure-activity relationship (QSAR) analysis. Materials and Methods Materials.