Introduction
Dietary factors play an important role in human health and in the development of certain diseases. Many
kinds of traditional medicines have been used over a long period of time in Asia. However, the active principles in
traditional medicines are still unknown. In order to realize the full potential of these medicines, it is important to
isolate the specific compounds and to identify the chief active principles in them (Kaur
et al
., 2006).
Total phenolic compounds are plant metabolites widely spread throughout the plant kingdom. Recent
interest in phenolic content stems from their potential protective role, through ingestion of fruits and vegetables,
against oxidative damage diseases (coronary heart disease, stroke, and cancers) (Block
et al
., 1992). Total phenolic
compounds are essential for the growth and reproduction of plants, and are produced as a response for defending
injured plants against pathogens. The importance of antioxidant activities of total phenolic compounds and their
possible usage in processed foods as a natural antioxidant have reached a new high in recent years.
The purpose of this study was to evaluate a variety of traditional medicinal plants against cancers, diabetes
and allergies that were growing in the same location with respect to their total phenolic content and antioxidant
activity to find new potential sources of natural antioxidants.
Materials and methods
Chemicals and reagents
Sodium carbonate were purchased from Riedel-de Haën, Seelze, Germany. Folin-Ciocalteu’s reagent (FCR)
were from Carlo Erba Reagenti (Milano, Italy).
Extraction
Plant samples were collected in January 2011. Plants were washed, dried in hot-air oven at 50°C for 72 h
and powdered in a blender for 1 min at maximal speed then divided into smaller aliquots and frozen at -20°C until use.
Each crude (100 g) was extracted into 2 cycles in 70% (v/v) ethanol and water at 60°C, 48 h by using Büchi B-811
universal extraction system then evaporated, lyophilized and stored at -80°C for further investigation.
Determination of total phenolic compounds
Total phenolic compounds were determined the Folin-Ciocalteau colorimetric method using gallic acid as a
standard by a modified procedure of Singleton
et al
. (1999). For the preparation of calibration curve, 0.5 mL aliquots
of 50-300 µg/mL ethanolic gallic acid solution (50% ethanol, w/v) were mixed with 2.5 mL of Folin-Ciocalteau
reagent, FCR and 2 mL of 2% (w/v) sodium carbonate solution. Dried crudes were dissolved in 50% (v/v) ethanol to a
final concentration of 20 mg/mL. The sample solutions (0.5 mL) were mixed with the same reagents as described
above. The absorbance of standard and samples were then measured at 760 nm after standing at room temperature
(25°C) for 30 min. All the tests were performed in triplicate. Results were expressed as µg gallic acid equivalents per
g. Data were subjected to analysis of variance, and means were compared by least significant difference (LSD).
Differences at p < 0.05 were considered to be significant.
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