NMR and mass spectral studies of ‘Abaliose’ – a novel hexasaccharide isolated from <i>Bubalus bubalis</i> milk

Milk oligosaccharides confer unique health benefits to the neonates. Recent studies show that these milk oligosaccharides (MO) show potent medicinal activities such as anti-tumour, immunostimulant, anti-complimentary, anti-cancerous, anti-inflammatory, anti-diabetic and active against virus. Buffalo milk oligosaccharide induces significant stimulation of antibody, delayed type hypersensitivity and non-specific immune response. Keeping the biological activities of buffalo MOs in mind, it was processed by the method developed by Deepak et al. Thereafter its purification involving chromatographic techniques, resulted in isolation of a novel hexasaccharide ‘Abaliose’. Three-dimensional structure of this oligosaccharide was elucidated by HSQC, TOCSY, COSY and HMBC NMR experiments and mass spectrometric data confirming it to be a Novel hexasaccharide made up of Glc, Gal, GlcNHAc and GalNHAc linked together by β-(1→4), β-(1→3) and β-(1→2) glycosidic linkages (Figure 1).乳寡糖对新生儿具有独特的健康益处。近期研究表明，这类乳寡糖（milk oligosaccharides, MO）具备多种强效药理活性，包括抗肿瘤、免疫刺激、抗补体、抗癌、抗炎、抗糖尿病以及抗病毒活性。水牛乳寡糖可显著刺激抗体生成、迟发型超敏反应与非特异性免疫应答。基于水牛乳寡糖的上述生物学活性，研究人员采用Deepak等人开发的方法对其进行了处理，随后通过色谱技术开展纯化，成功分离得到一种新型六糖“Abaliose”。本研究通过HSQC、TOCSY、COSY及HMBC核磁共振（NMR）实验，结合质谱数据解析了该寡糖的三维结构，证实其为一种由葡萄糖（Glc）、半乳糖（Gal）、N-乙酰葡糖胺（GlcNHAc）和N-乙酰半乳糖胺（GalNHAc）通过β-(1→4)、β-(1→3)与β-(1→2)糖苷键连接而成的新型六糖（图1）。