Food-derived Trp-rich oligopeptides: Production, bioactivities, and structure-function relationship

Tryptophan (Trp) has been extensively studied for many years due to its unique and multifaceted role in human health and diseases. Trp-rich oligopeptides (TROs) not only serve as a source of dietary Trp but also exhibit their own unique bioactivities. Comprehensive reviews of the production, bioactivity and structure-activity relationships of TROs are currently lacking. This article provides a comprehensive overview of recent research on TROs to gain a deeper understanding of the potential food sources of TROs, viable industrial production methods for TROs, and the working mechanisms underlying the bioactivities of TROs. The challenges or obstacles in comparing the published results are elucidated, as the published studies used varied raw materials, employed different processing and analysis methods, and utilize different in vivo or in vitro systems. This review delves into the diverse bioactivities of TROs as well as the underlying working mechanisms and possible structure-activity relationships. It also explains the existing knowledge gaps and the challenges potentially encountered during tailoring the functionalities of TROs as bioactive compounds and utilizing the TROs in foods as functional ingredients. The key findings of this review explain the growing interest in the health benefits of TROs and the mechanisms underlying these benefits, such as antioxidant, anti-inflammatory, antihypertensive, hyperuricemia-suppressing, antidiabetic and neuroprotective effect. It was found that bioinformatics and peptidomics approaches are increasingly used as promising screening methods to identify TROs with bioactivities. It can be confirmed that food-derived TROs are an important subset of small peptides mainly composed of dipeptides and tripeptides and that they exhibit various bioactivities with their TRP residues having preferred positions in biological systems (e.g. the membrane interface). While these findings indicate the potential of TROs as functional foods/ingredients or dietary supplements, further in vivo studies of TROs using animal models or through human trials are definitely needed to validate the potential health benefits of TROs and development of TRO-based functional products to support foods and dietary supplements.