Effect of Lychee Fruit Extract (Oligonol) on Peripheral Circulation, a Pilot Study Skin Thermography Demonstrates Vasodilation Effects of Polyphenol

Natural Medicine Journal. 2014;6(7)


A trial to assess the effect of Oligonol on peripheral circulation was compared with a placebo in healthy adults. The underlying mechanism for Oligonol’s effect on circulation may be a result of increased nitric oxide (NO) production. Previous studies have indicated that polyphenols might regulate NO production by the protein kinase C-dependent nicotinamide adenine dinucleotide phosphateoxidase activation pathway. A NO-dependent mechanism is further supported by the previous finding that Oligonol enhanced NO production by regulating phosphorylation and dephosphorylation of endothelial NO synthase (eNOS) 28. The effect of Oligonol on NO production was investigated in bradykinin-stimulated vascular endothelial cells under high-glucose conditions. Oligonol prevented the impairment of eNOS activity induced by high glucose through reversing altered eNOS phosphorylation status. Briefly, when endothelial cells were stimulated by bradykinin (30 nm) and cultured in a medium with a high concentration of glucose, NO production was decreased. However, the reduction was recovered by treatment with Oligonol.

Study Design

The effect of Oligonol on peripheral circulation was measured as skin temperature changes by infrared thermography. Six healthy subjects (3 male, 3 female; 28–40 years old; body mass index &lt 25) were supplemented with 50 mg of Oligonol and a placebo (malt extract, dextrin) alternatively on different days. Subjects fasted for 12 hours prior the test and changed into clothing designed for skin thermography measurement. Subjects were asked to stay calm and rest for 60 minutes in a temperature-controlled room (room temperature 26° C ± 1° C, humidity 50%) prior to oral administration of the samples. Thermographic measurements of changes in skin temperature were completed immediately before the oral dose and every 30 minutes after for up to 120 minutes. The areas of interest for the thermographic measurements were the neck, shoulder, and right palm. A paired t-test was used to determine skin temperature differences within subjects between time periods. Welch’s t-test was used to compare skin temperature between groups. A level of p = .05 was recognized as statistically significant. Values are presented as mean and standard error of the mean.


Thirty minutes following Oligonol ingestion, thermographic measurements showed a significant temperature increase in the right palm in the Oligonol group compared with the placebo group. Temperature changes between groups were significantly different at 30 minutes and 60 minutes. The temperature remained significantly above base line levels for up to 120 minutes in the Oligonol group. While thermographic measurements of the neck and shoulder trended toward an increase in temperature in the Oligonol group compared with placebo, there were no significant differences between groups. Within each treatment group, the temperature increased and remained significantly above the base line temperature through 120 minutes. The results showed a significant elevation of body surface temperature in the beforeand- after thermographs in the palms of all subjects in the Oligonol group, which suggests peripheral blood flow improvement in healthy people. The results of thermographic measurements of the neck and shoulder showed no significant differences between groups. However, there was a significant increase in both groups compared with the base line.


Oligonol improves peripheral circulation as measured by skin temperature changes using infrared thermography. The elevation in temperature is thought to be a result of the increase of the blood through the vascular smooth muscle, resulting from polyphenol-enhanced NO production in the vascular endothelium. This mechanism may underlie the beneficial vascular health effects of Oligonol. Further studies with increased sample size are warranted.