Neoxanthin in young vegetable leaves prevents fat accumulation in differentiated adipocytes

The present study aimed to investigate the effect of young leaves on fat accumulation in differentiated 3T3-L1 adipocytes. A potent preventive effect on fat accumulation was observed in fractions of young leaves of spinach, beet, and arugula extracted with a low-polarity solvent (hexane:acetone:ethanol:toluene = 10:6:7:6). This effect was seemingly associated with the leaf carotenoid content, including lutein, β-carotene, and neoxanthin. Among these, only neoxanthin, with the characteristic structure of 5,6-monoepoxide and an allenic bond, significantly prevented fat accumulation in a dose-dependent manner. The preventive effect and carotenoid content, including neoxanthin, of these young leaves did not differ from those of the corresponding adult leaves. Therefore, our study demonstrated that young vegetable leaves, such as spinach, beet, and arugula leaves, contained neoxanthin, which prevented fat accumulation in adipocytes in vitro. In the future, the effectiveness of such young leaves and neoxanthin should be investigated in vivo.

Comparison of (-)-epigallocatechin-3-O-gallate (EGCG) and O-methyl EGCG bioavailability in rats

(-)-Epigallocatechin-3-O-(3-O-methyl)gallate (EGCG3″Me) and (-)-epigallocatechin-3-O-(4-O-methyl)gallate (EGCG4″Me) are O-methyl derivatives of (-)-epigallocatechin-3-O-gallate (EGCG) present in tea cultivars such as Benifuuki. Although O-methyl EGCGs have various bioactivities, their bioavailabilities have not been determined. In this study, we compared the bioavailability of EGCG and O-methyl EGCGs in rats, and clarified the pharmacokinetics of O-methyl EGCGs. Following oral administration (100 mg/kg), the areas under the concentration-time curves (AUCs) for EGCG, EGCG3″Me, and EGCG4″Me were 39.6 ± 14.2 µg·h/L, 317.2 ± 43.7 µg·h/L, and 51.9 ± 11.0 µg·h/L, respectively. The AUC after intravenous administration (10 mg/kg) was 2772 ± 480 µg·h/L for EGCG, 8209 ± 549 µg·h/L for EGCG3″Me, and 2465 ± 262 µg·h/L for EGCG4″Me. The bioavailability of EGCG3″Me (0.38%) was the highest (EGCG: 0.14% and EGCG4″Me: 0.21%). The distribution volume of EGCG3″Me (0.26 ± 0.02 L/kg) was the lowest (EGCG: 0.94 ± 0.16 L/kg and EGCG4″Me: 0.93 ± 0.14 L/kg). These results suggested that the higher AUC of EGCG3″Me after oral administration was related to its high bioavailability and low distribution volume. These findings supported the stronger bioactivity of EGCG3″Me in vivo.

O-methylated theaflavins suppress the intracellular accumulation of triglycerides from terminally differentiated human visceral adipocytes

A known O-methylated theaflavin, theaflavin 3-O-(3-O-methyl)gallate (3MeTF3G), and the new theaflavin 3-O-(3,5-di-O-methyl)gallate (3,5diMeTF3G) were synthesized via the O-methylation of theaflavin 3-O-gallate (TF3G). Both 3MeTF3G and 3,5diMeTF3G are more stable than TF3G at pH 7.5 in the order 3,5diMeTF3G > 3MeTF3G > TF3G. The inhibitory effects of these compounds on the intracellular accumulation of triglycerides from terminally differentiated human visceral adipocytes were investigated. Compound 3MeTF3G exhibited an inhibitory effect similar to that of TF3G at 3 μM and a slightly lower effect than that of TF3G at 10 μM. The result suggested that the degradants and oxidatively polymerized products of TF3G may also have inhibitory effects. For cells treated with 3,5diMeTF3G at 3 and 10 μM, intracellular triglyceride accumulation was dose dependent and significantly lower compared with that for other compounds. It was suggested that the higher effect of 3,5diMeTF3G was due to its higher stability and likely improved absorption owing to di-O-methylation.

Antihypertensive effect of Benifuuki tea containing O-methylated EGCG

Benifuuki is a tea cultivar with an antiallergic effect stronger than that of Yabukita tea, the most popular green tea cultivar consumed in Japan. The effective compound is (-)-epigallocatechin-3-O-(3-O-methyl)gallate (EGCG3''Me), an O-methylated derivative of EGCG. This study examined the antihypertensive effects of EGCG3''Me and Benifuuki tea. First, it was determined that EGCG3''Me has a significant inhibitory effect on the activity of angiotensin I-converting enzyme (ACE). Second, clinical trials showed that Benifuuki tea suppressed high blood pressure to a greater extent than green tea that did not contain EGCG3''Me after equal amounts of tea catechins were consumed for 8 weeks. The effect of Benifuuki tea on human hypertension is mainly the result of the strong inhibitory effect of EGCG3''Me on ACE activity, its high rate of absorption, and its stability in the blood.