Reactive oxygen species (ROS) are recognized
to be involved in the pathogenesis of various
diseases such as cancer, atherosclerosis, diabetes
mellitus, arthritis, ischemia/reperfusion disorder.
It has been shown that appropriate intake of
antioxidants is preventive from such ROSmediated
diseases. In the Okinawa Islands medicinal plants have been used not only as folk medicine but also as food and drink. It was expected that edible medicinal plants or traditional foods with antioxidant action may play a role for prevention of free radical mediated diseases or health promotion. In the present study antioxidant action and active components from these plants and foods were investigated. Antioxidant action was evaluated by using electron spin resonance (ESR) spectrometer and chemiluminescence (CL) analyzer. Among 90 plants, antioxidant action was found in 66 species and 11 plants showed strong scavenging action for
superoxide and hydroxyl radicals. Okinawan
vegetables of 18 species (some of them are
medicinal plants) also possessed strong antioxidant
action. In addition, the antioxidant action of molds, which have been used for fermentation of food or drink, was evaluated and found in Monascus anka and Aspergillus kawachi.

Components with antioxidant action of the
plants were isolated and identified: Six quercetin
derivatives (-3-glucoside, -3-galactoside, 3-xyloside, 3-arabinopyranoside, -3-arabinofuranoside and -3-rhamnoside) from Psidium guajava (called Guava), eridictyol, rhamnetin, eupatolitin, and 5,6,7- trihydroxy-2-(4-hydroxyphenoxy)chromenonefrom
Artemisia campestris (Ryukyuyomogi), gallic acid
from Limonium wrightii (Ukonisomatsu), and
chlorogenic acid from Peucedanum japonicum
(Botanboufu). Dimerumic acid was identified as
the antioxidant of the mold Monascus anka.
Pharmacological actions of these plants and
molds were examined: hepatoprotective action
against chemically induced liver injuries, diuretic
action, antidiabetic action or depression of nitric
oxide formation were demonstrated. Some
antioxidants isolated showed drug metabolizing
enzyme inhibitory action. For example, Curcuma
longa (called Ukon) involving curcumin as the
antioxidant is a very popular drink in Okinawa.
Recently Guava drink was developed by an
Okinawan Company. Our research suggests
that these plants or foods are good sources of
natural antioxidants.
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