Activity of hydrogenated curcuminoid on Pd/C catalyst and its antibacterial activity against Staphylococcus aureus and Streptococcus mutans

Turmeric (Curcuma longa) has been known for its benefit as one of medicinal herbs. Curcuminoids, the active compounds in turmeric, consist of three structurally related compounds, curcumin, demethoxycurcumin, and bisdemethoxycurcumin. Curcuminoid has been reported to be effective for the treatment of chronic gingivitis and hence it can be a potential candidate to be used as an active ingredient for antimicrobial in a mouthwash. However, its yellow color has hampered its application as a mouthwash as it may cause the aesthetical problem to the teeth. In this study, curcuminoids, obtained from Soxhlet extraction of turmeric powder, were reduced by hydrogenation on Pd/C catalyst to remove the color. TLC analysis revealed that the products consist of three compounds as expected. The product was purified from unreacted curcuminoids by column chromatography on silica gel, to obtain a colorless product with percent conversion of 23.45 %. These three compounds were characterized by Uv-Vis spectrophotometer resulted in three peaks in three different wavelengths: 282, 283 and 280 nm. Characterization with FT-IR spectrometer showed an increase intensity of CH-sp3 peak (2932 cm-1) when compared to the IR spectrum of standard curcuminoids, and the shift in C-O absorption (1231 cm-1), indicated the existence of methoxy groups that can distinguish one to the other compounds. These three compounds then were evaluated for their antibacterial activity against Staphylococcus aureus and Streptococcus mutans. The result showed that the tetrahydrocurcumin had moderate antibacterial activity against S. aureus with inhibition zone of 5.5 mm and tetrahydro desmethoxycurcumin also showed moderate antibacterial activity against S. mutans with inhibition zone of 5.5 mm.