Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/11/2007
Publication Date: 7/18/2007
Citation: Wang, C.Y., Wang, S.Y., Yin, J., Parry, J., Yu. 2007. Enhancing Antioxidant, Antiproliferation, and Free Radical Scavenging Activities in Strawberries with Essential Oils. Journal of Agricultural Food & Chemistry. 55:6527-6532. Interpretive Summary: Diets rich in fruits and vegetables may reduce the risk of some types of cancer and other chronic diseases. The main reason for health benefits of fruits and vegetables is they contain numerous vitamins and other beneficial natural compounds called antioxidants. However, little is known about changes of antioxidant levels in fresh fruits and vegetables after harvest or how to maintain or increase these levels. This is important because antioxidant content can decline rapidly after harvest due to mishandling. In our experiments, we treated strawberry fruit with natural essential oils immediately after harvest and found that this treatment helped maintain levels of antioxidants as well as reduce decay and lengthen storage life of berry fruit. Therefore, it is possible that both health benefits and shelf-life can be improved by postharvest treatment with essential oils. This information should be of interest to other scientists and can be useful to the berry industry and will also be beneficial to consumers.
Technical Abstract: Several natural antimicrobial compounds derived from essential oils of plants were investigated for their efficacies in inhibiting decay and extending shelf life of strawberries (Fragaria x ananassas Duch.). The severity of decay in strawberries stored at 10 oC was significantly reduced by treatment with thymol. Treatments with menthol or eugenol also suppressed the fungal growth but to a lesser extent. All of these three natural antimicrobial compounds extended shelf life of strawberries as compared to the control. Strawberries treated with thymol, menthol, or eugenol also maintained better fruit quality with higher levels of sugars, organic acids, phenolics, anthocyanins, flavonoids, and oxygen radical absorbance capacity (ORAC) than the untreated fruits. The free radical scavenging properties of strawberry fruit were evaluated against DPPH, hydroxyl, and superoxide radicals using electron spin resonance (ESR) measurements. Higher radical scavenging capacities were found against DPPH and HO in all treated fruit, particularly in berries treated with thymol, than those in control samples. In addition, strawberry extracts were evaluated for their antiproliferative effects using HT-29 colon cancer cells. Extracts from all treated fruit significantly inhibited HT-29 cell proliferation compared to those from control fruit. These data provide evidence that in addition to possessing antimicrobial activity, the essential oils also increase free radical scavenging capacity and antiproliferative activity in fruit and, in turn, enhance the resistance of fruit tissues to deterioration and spoilage.