Garlic (Allium sativum L.) is traditionally believed to have many health benefits and has been used to prevent many diseases such as the common flu and gastrointestinal disorders. Anecdotal evidence in China suggests that the successful treatment of gastrointestinal diseases by the consumption of fried garlic and eggs may be related to its function of improving the human gastrointestinal environment. Interests in the analysis of garlic components such as essential oil, selenium, amino acids and their contributions to the claimed benefits have grown in recent years [1], [2] and [3]. Garlic essential oil is known to have antimicrobial activities which may help to inhibit the growth of some pathogens in the gastrointestinal tract [4]. It has been reported that some garlic fermenting Lactobacillus strains were isolated from fermented fish foods [5]. Actually, garlic was found to contain fructans 12.5% to 23.5% on a wet weight basis, and more than 75% on a dry weight basis [6] and [7]. As a major component of garlic, fructan may contribute to the protection against gastrointestinal diseases by improving the microbial gastrointestinal environment. Therefore, it was interesting to investigate the prebiotic effectiveness of garlic fructan (GF) on human intestinal microflora.
Garlic fructan is an insulin-type fructan that belongs to the neokestose family, and has a (21)-linked ?-d-Fru f backbone with a (26)-linked ?-d-Fru f side chains. A structural model for high molecular weight garlic fructan estimated a degree of polymerization (DP) of about 58 based on its molecular weight and fructose: glucose ratio (about 15:1) [6] and [7]. Because of the ? (21) linkage of fructose monomers, fructans cannot be digested by intestinal enzymes, and thus, they are classified as “non-digestible” carbohydrates [8] and [9]. In the colon, some fructans (inulin-type) are rapidly fermented to produce short chain fatty acids (SCFA) that explain some of the systemic effects of fructans. Bifidobacteria (and possibly a few other genera) are preferentially stimulated to grow in the presence of fructans in the colon, resulting in significant changes in the composition of the gut microflora by increasing the number of potentially health-promoting bacteria and reducing the number of potentially harmful species [9], [10], [11] and [12].
In this study, neutral GFs were prepared by ethanol fractionation precipitation. They were added as the sole carbon source into an in vitro batch fermentation system inoculated with human fecal bacteria prepared from the feces of 3 human volunteers. Changes of total anaerobic bacteria, bifidobacteria population, fecal microflora and pH were investigated.