Obesity is an important topic in the world of public health and preventive medicine. Inhibition of preadipocyte proliferation plays an important role in the mechanisms of proposed antiobesity. In this in vitro study, the inhibitory effect of phenolic acids on 3T3-L1 preadipocytes was evaluated, and a relationship analysis was then conducted. The results showed that the addition of phenolic acids to the growth medium decreased the cell population growth of 3T3-L1 preadipocytes. The IC50 values of chlorogenic acid, gallic acid, o-coumaric acid and m-coumaric acid on 3T3-L1 preadipocytes were 72.3, 43.3, 48.2, and 49.2 microM, respectively. A relationship analysis indicated that there is a significant linear correlation between the influence of phenolic acids on cell population growth and their antioxidant activity (r = 0.77, p < 0.01). The cell cycle assay indicated that the treatment of 3T3-L1 preadipocytes with chlorogenic acid, o-coumaric acid, and m-coumaric acid caused cell cycle arrest in the G1 phase. Gallic acid did not affect the cell cycle profile; however, it increased the number of apoptotic cells (sub-G1 phase) in a time- and dose-dependent manner. Annexin V-fluorescein isothiocyanate (FITC)-propidium iodide (PI) apoptosis flow cytometric assay showed that gallic acid increased the number of early apoptotic (annexin V-FITC+/PI-) and late apoptotic cells (annexin V-FITC+/PI+) but not necrotic cells (annexin V-FITC-/PI+). The treatment of cells with gallic acid caused the loss of mitochondrial membrane potential (delta psi(m)). These results indicate that the inhibition of preadipocyte population growth by some phenolic acids might have further implication in in vivo antiobesity effects.

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The pro-oxidative properties of the four flavonoids, quercetin, morin, naringenin and hesperetin, in human lymphocyte system were investigated. Naringenin and hesperetin accelerated the oxidation of deoxyribose induced by Fe(3+)/H(2)O(2) in a concentration range of 0-200 microM, but quercetin and morin decreased it when the concentration was greater than 100 microM. The generation of hydrogen peroxide and the superoxide anion and the production of TBARS in lymphocytes were increased with increasing concentration of a flavonoid. Cell membrane protein thiols of the lymphocytes decreased when treated with the four flavonoids. Quercetin and hesperetin had no significant effect (p>0.05) on the activity of glutathione reductase, but morin and naringenin could inhibit the activity of the enzyme at a concentration of 200 microM, when compared to the control group. The glutathione S-transferase activity was slightly decreased by treatment with each of the four flavonoids only at a concentration of 200 microM. Therefore, the DNA damage in lymphocytes induced by the flavonoids in the model system might have been due to their stimulation of oxidative stress in the lymphocytes, which resulted in the decrease of cell membrane protein thiols, increase of lipid peroxidation in cell membrane and in the influence of the antioxidative enzyme activities.