Study of stingless bee (Heterotrigona itama) propolis using LC-MS/MS and TGA-FTIR

Abstract

Propolis, especially meliponini propolis is getting more popular in the functional food market, mainly due to its pharmacological importance. The quality of propolis is largely dependent upon the extraction technology and its solvent system. The present study investigated the performance of propolis extraction from maceration with and without ultrasonic pretreatment (30 min) in both water and 20% ethanol systems. Maceration was chosen to avoid degradation of heat sensitive compounds. Ultrasonic pretreatment was introduced to enhance propolis extraction from recalcitrant raw material. The yield of propolis was 4.0-5.5%. The results found that maceration with ultrasonic pretreatment, especially in aqueous ethanol increased the phenolics (17.043 mg GA/g), tannins (5.411 mg GA/g) and flavonoids (0.83 mg Q/g) content, as well as antioxidant capacity of propolis (80% at 1 mg/mL). Mass spectral based principal component analysis revealed that solvent system had higher effect (> 30%) on the variance of propolis quality rather than extraction technology. The variance of chemical composition had also led to the difference of antioxidant capacity among propolis samples. Alcohol precipitation would remove polymeric substance from propolis which was then characterised by thermogravimetric analysis coupled with Fourier transform infrared spectrometer (TGA-FTIR) after acid hydrolysis. The substance was putatively identified as hygroscopic lignocelluloses (14.4% moisture, 36.6% hemicelluloses and celluloses, 40% lignins), and started to decompose at 203°C, involving 4 steps of degradation mechanism at the highest derivative weight of 12.09%/min.