Bio-guided fractionation of black pepper essential oil by means of preparative gas chromatography

Recent studies have shown that essential oils (EOs) from spices are effective in reducing high blood glucose levels, with β-caryophyllene (BCP) emerging as one of the most promising bioactive compounds. Despite the increasing interest in this field, few studies in the literature have elucidated the link between sample components and their resulting biological activities. In this paper, a detailed investigation was carried out, using a black pepper EO as a case study, and α-glucosidase as biological target. Initial biological assays showed very similar activities between the entire EO and the corresponding amount of BCP in the EO on α-glucosidase. These outcomes confirmed the manifest role of BCP, and further suggested that EO's fractionation could help to unravel the complex interactions among terpene families, BCP, and the biological target. As a first step, a suitable preparative GC method was developed to enable the effective and rapid isolation of the separated monoterpene and sesquiterpene families for subsequent biological assays. The biological outcomes bio-guided consequent fractionation procedures, which were aimed at understanding the role of BCP in the overall sesquiterpene family. Consequently, the use of multidimensional preparative GC guaranteed the effective isolation of the sesquiterpene family without BCP, underscoring its relevant role in this fraction. In a complementary approach, the sesquiterpene family was further fractionated to understand potential enhancing/inhibitory effects with BCP. To the best of authors' knowledge, this paper represents the first instance in the literature where preparative gas chromatography has been employed as an analytical approach to carry out a bio-guided fractionation of EOs.