Abstract: Geraniin is a naturally occurring hydrolysable ellagitannin with significant biological activity. Earlier, we have demonstrated that rambutan peel is rich in geraniin. In this study, the rapid separation and purification of geraniin from rambutan peel polyphenols (RPP) extract was carried out by medium-pressure liquid chromatography (MPLC) with a reversed-phase C18 column system and preparative high-performance liquid chromatography (HPLC). The identification of geraniin and its thermal degradation products was conducted by ultra-performance liquid chromatography-quadrupole-orbitirp-mass spectrometry (UPLC-Q-Orbitrap-MS). The results showed that the content of geraniin in freeze-dried rambutan peel was 12.67 g/100 g (on a dry matter basis). Geraniin with a purity of 95.63% and a yield of 6.00% (on the basis of the dry mass of rambutan peel) was obtained. The purified geraniin showed instability to heating. The percentage of degradation loss was 17.13% after treatment at 60 ℃ for 10 hours, and was 73.97% after treatment at 100 ℃ for 2 hours. In the degradation products of geraniin, gallic acid, corilagin, hexahydroxybiphthalic acid, brevifolin carboxylic acid, galloyl-bis-HHDP-glucose, ellagic acid, and brevifolin were detected as phenols with lower molecular mass. The results of the study can provide a discussion on the controlled degradation and bioavailability of geraniin.

Key words: rambutan peel; geraniin; ellagitannin; separation and purification; thermal stability