Plant extracts obtained from medicinal plants by steam distillation
or solvent extraction have been used to treat various
diseases since ancient times, particularly in Asian countries.1
They have continued to be used even after the development of
modern medicines. To date, over 7000 medicinal plants or
herbs have been utilized by 80% of the world’s population.2
Many recent studies demonstrate the medicinal activities, in
particular antioxidant activities, of natural plant materials
against various diseases: including atherosclerosis, cancer, diabetes, Alzheimer’s, HIV, Parkinson’s, and cataracts.3 Therefore, antioxidants found in natural plants, such as vitamin E (α-tocopherol), vitamin C, and polyphenols/flavonoids,4 have received much attention as alternative medicines preventing these diseases. For example, a recent symposium summarizes the effects of polyphenols, which are relatively less-volatile chemicals, on human health.