Abstract

Background: Orthosiphon stamineus is a medicinal herb rich in caffeic acid derivatives. Rosmarinic acid is one of the caffeic acid-based phytochemicals which is also well-known for its antioxidant and anti-inflammatory properties.

Objective: This study was focused on the preparation of rosmarinic acid-rich fraction to enhance the antioxidant capacity of O. stamineus.

Method: The rosmarinic acid-rich fraction was prepared by using an integrated technique of reflux extraction and column chromatography. The concentration of ethanol was varied from 0-100 %v/v to optimize the yield of rosmarinic acid in the fraction.

Results: This technique increased the rosmarinic acid content from 0.14 %w/w in the dried whole plant to 1.9 %w/w in the crude extract till 4.1 %w/w in the 80 %v/v ethanol fraction. The consecutive elution of packed column also produced eupatorin-rich fraction from 0.0008 %w/w in the dried whole plant to 0.17 %w/w in the crude extract and 0.5 %w/w in the 40 %v/v ethanol fraction. The increment of rosmarinic acid content enhanced the radical scavenging activity in the fractions. The IC₅₀ was significantly decreased from 2424 to 37.7 ppm for the crude extract and its 80 %v/v ethanol fraction, respectively. Therefore, the increase of rosmarinic acid content also increased the antioxidant capacity of the plant extract.

Conclusion: This rosmarinic acid-rich fraction could be further developed into various useful herbal products for the benefits of mankind.

Keywords: Herbal plant, Orthosiphon stamineus, rosmarinic acid, eupatorin, reflux extraction, column chromatography.