Antioxidant activity, phenolic and flavonoid content of some Philippine fruits and vegetables

The antioxidant activity, total phenolic content and total flavonoids content of some Philippine fruits and vegetables were determined. Some of the fruit samples are underutilized fruits and the vegetable samples examined are underutilized in the country. The antioxidant activity of the fruits examined ranged from 106.12% to 76.70% with Kalamyas [Averrhoa balimbi] exhibiting the highest activity followed by Katmon, santol, balimbing and bignay. Pomelo, lychee and durian showed negative antioxidant values indicating that these fruit samples had pro-oxidant activity. Correlation analyses were conducted to determine the realationship between antioxidant activity, total phenolic content and total flavonoids content. Significant positive correlations were observed for total phenolics and total flavonoids content indicating that a large fraction of the total phenolics are flavonoids. Antioxidants activity and total phenolics content were weakly but positively correlated. The correlation between antioxidant activity and total flavonoids content was positive but was statistically insignificant. The alpha-tocopherol equivalent expressed in IU, for each gram sample was computed and approximations were calculated using reference Vitamin E solution (1 mg/mL alpha-tocopherol). The quantity of a sample that would approximately contain 400 IU of alpha-tocopherol was also computed. Vitamin E supplement capsules usually contain this amount of alpha-tocopherol. The amounts of fruit samples computed may possibly exhibit similar protection afforded by vitamin E supplements. It is however, pointed out that the values given are simply approximations and should not be considered as bases for therapeutic purposes. Santol, guavas, chico, kalamyas and kamansi were blanched in boiling water for 6 minutes and the antioxidant activity, total phenolic content and total flavonoid content were monitored every 2 minutes. Citrus juice was pasteurized for a period of 120 seconds and was likewise monitored for changes in antioxidant activity, total phenolics content and total flavonoids content. The results were varied and thus, this indicated that the effect of heat treatment cannot really be predicted. An increasing trend in antioxidant activity was observed for santol and chico while decreasing trend was observed for guavas and kamansi and minimal changes with prolonged heating were observed for kalamyas and citrus. A large increase in total phenolics content and total flavonoids content was observed in the first 5 minutes of blanching of santol and the levels were maintained up till the end of blanching. A decreasing trend in phenolics and flavonoids levels from zero to 20 minutes of blanching was observed for chico and kamansi. Even with the increase or decrease with increase in temperature may vary with the types of sample, the antioxidants activity and the amounts of phenolics may still be retained in significant levels. A wide range of antioxidants activity values was also observed on vegetables that were analyzed. Antioxidant activity of the samples ranged from 6.24% inhibition to 70.09% inhibition. Various factors may account for the variations in the values. Kinalaan had the highest antioxidant activity while labong [edible bamboo shoot] had a moderate level of activity. The other vegetables analyzed (like edible ferns, cassava, malunggay and squashes of the leafy vegetables) had loss antioxidant activity. The total phenolics content of cassava leaves had the highest total phenolics content while malunggay pods had the lowest amount. Of the other vegetables category, labong had the highest total phenolic content. Kadyos [pigeon pea, Cajanus cajan] gave the lowest total phenolics content of all the vegetable samples examined. Representative samples of the vegetables were subjected to blanching for 6 minutes in boiling water. The results showed that the decrease in total phenolics content paralleled the decrease antioxidant activity. Variations however, were noted for total flavonoids content. Loss in flavonoid content was quite large for squash leaves but was relatively low for cassava leaves. The total flavonoid content of lima bean leaves did not significantly charge with blanching while that of pepper leaves increased. The results obtained indicate that the fruits and underutilized vegetables of the Philippines have considerable antioxidant activity, total phenolics content and total flavonoid content. Filipinos have a wide array for fruits and vegetables that could provide them with the phytochemicals that could benefit their health and well-being.