We previously reported that kiwi fruit is rich in polyphenols and has immunostimulatory activity. Polyphenols are widely known for having anti-oxidant effects. We also revealed potential anti-oxidant effects of kiwi fruit in vivo by oral administration to mice. Here, we compared the anti-oxidant effects of kiwi fruit with those of other fruits in vitro. Then, we examined the inhibitory effects of kiwi fruit on oxidation in the human body. There are two varieties of kiwi fruit, green kiwi and gold kiwi. We also examined variation between these varieties. Comparison of the anti-oxidant effects in vitro demonstrated that kiwi fruit had stronger anti-oxidant effects than orange and grapefruit, which are rich in vitamin C; gold kiwi had the strongest anti-oxidant effects. Kiwi fruit inhibited oxidation of biological substances in the human body. In particular, kiwi fruit may inhibit early lipid oxidation. In this study, kiwi fruit had strong anti-oxidant effects and may prevent the development and deterioration of diseases caused by oxidative stress.

A beta-D-glucan obtained from Aureobasidium pullulans (AP-FBG) exhibits various biological activities: it exhibits antitumour and antiosteoporotic effects and prevents food allergies. An unambiguous structural characterisation of AP-FBG is still awaited. The biological effects of beta-D-glucan are known to depend on its primary structures, conformation, and molecular weight. Here, we elucidate the primary structure of AP-FBG by NMR spectroscopy, and evaluate its biological activities. Its structure was shown to comprise a mixture of a 1-3-beta-D-glucan backbone with single 1-6-beta-D-glucopyranosyl side-branching units every two residues (major structure) and a 1-3-beta-D-glucan backbone with single 1-6-beta-D-glucopyranosyl side-branching units every three residues (minor structure). Furthermore, this beta-D-glucan exhibited immunostimulatory effects such as the accumulation of immune cells and priming effects against enterobacterium. To our knowledge, 1-3-beta-glucans like AP-FBG with such a high number of 1-6-beta-glucopyranosyl side branching have a unique structure; nevertheless, many 1-3-beta-glucans were isolated from various sources, e.g. fungi, bacteria, and plants.

We have been investigating the immunopotentiating activity (biological response modifier (BRM)-like activity) of different fruits and attempting to clarify whether the level of this activity is consistent with the content of vitamins or other major nutrients in these fruit. In this study, we focused on kiwi fruit, which contains vitamin C and polyphenol and has a high BRM-like activity and anti-oxidant activity. We evaluated differences in this activity according to the strain and maturity. To determine the antioxidant effects of oral kiwi fruit intraperitoneal administration, mice were administered kiwi fruit juice. It was found that the BRM-like activity of green kiwi fruit was slightly higher than that of gold kiwi fruit, but the differences were slight between strains and maturity level. After oral administration of kiwi fruit juice to mice, cytokine production increased. The evaluation of urinary oxidative stress markers revealed marked inhibition of in vivo oxidative stress following oral kiwi fruit administration. These results suggest that kiwi fruit intake has beneficial effects on the body, increasing cytokine production and exerting antioxidant effects.

We have studied the neutrophil-increasing effects of fruits and vegetables and their priming effects on cytokine induction. Among fruits, bananas exhibited the most marked priming effects. Therefore, we evaluated possible differences in the biological response modifier (BRM)-like activities of bananas (such as the effects on neutrophil accumulation and macrophage morphology, and the priming effects on cytokine induction), according to their strain and maturity, using a conventional strain and a strain for highland cultivation. As a result, the total intraperitoneal leukocyte count and % neutrophils increased in parallel with the concentration and maturity of banana extracts. These effects were more marked in the highland strain. After the addition of banana extracts, marked macrophage spreading was observed, and morphological changes differed according to the strain and maturity of bananas. The priming effects on TNF-α or IL-12 induction also differed according to the maturity and strain of bananas, and could also be confirmed after oral administration. These results suggest that banana intake is associated with various BRM-like activities, and these effects differ according to the maturity level of the bananas.

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