Providing scientific evidence for the use of dietary supplements: a case study in hepatoprotective plants

Medicinal plants have been used worldwide for centuries for nutritional and medicinal purposes. Among them, artichoke, milk thistle, and borututu are used for hepatoprotective effects, in the prevention and treatment of liver diseases. These plants are available in several formulations to an easier consumption, but there were no scientific studies supporting their quality and efficiency. In this connection, the present study was designed to clarify the differences between these formulations regarding to antioxidant, anti-hepatocellular carcinoma, and antimicrobial activities, as well as to their chemical composition, namely in sugars, organic acids, tocopherols, fatty acids, and phenolic compounds. The bioactivity of several mixtures containing different proportions of the mentioned formulations, as well as the effect of honey addition, were also assessed. Moreover, a preservation technique was applied to borututu dry material, gamma irradiation, and the samples were analysed in order to verify the effects of radiation on the chemical composition and bioactivity of borututu. In a general way, the studied plants revealed carbohydrates as the major components, with borututu revealing the highest energetic contribution with the highest content of carbohydrates and fat, sucrose and total sugars, shikimic and citric acids, a-, s-, d- and total tocopherols. Artichoke had the highest ash and protein contents, oxalic acid, SFA (mainly palmitic acid acid), and ? -tocopherol, as also the best n6/n3 ratio. Milk thistle showed the highest levels of fructose and glucose, quinic acid and total organic acids, PUFA, mainly linoleic acid, and the best PUFA/SFA ratio. Gamma irradiation did not appreciably affect borututu chemical composition, but the highest energetic contribution, total sugars, organic acids, tocopherols, and PUFA contents were detected in the sample irradiated at maximum dose (10 kGy), which indicates a preservation effect of the radiation to these molecules. This sample also presented the highest levels of total phenolics and flavonoids and the highest antioxidant activity. Irradiated samples kept the anti-hepatocellular carcinoma activity, despite the decrease observed in the methanolic extract prepared from the above referred sample. All of the single plant infusions, pills, and syrups revealed antioxidant properties with EC50 values lower than the daily recommended dose, but infusions and syrups showed higher antioxidant activity than pills. Regarding to the prepared mixtures, all of them revealed synergistic effects for antioxidant activity assays, and also in several assays regarding hepatocellular carcinoma toxicity, when compared to the activity of single plants. The results obtained in this work also proved the utility of honey addition to potentiate the antioxidant and cytoprotective properties of medicinal plant based infusions. Lastly, concerning the phenolic composition, these plants revealed to be a good source of these bioactive molecules, with prevalence of phenolic acids and flavonoids. Among the studied formulations, infusions presented the higher phenolic compounds amounts, with luteolin-7-O-glucuronide and luteolin-7-O-glucoside as the major flavonoids found in artichoke infusion, apigenin-7-O-glucuronide, luteolin-7-O-glucuronide, and apigenin-O-deoxyhexosyl-glucuronide as the main constituents of milk thistle infusion, and protocatechuic acid as the most abundant compound in borututu infusion. Accordingly, the antimicrobial activity of the three formulations followed the same tendency, with infusions presenting higher activity, which can be related to the recognized antimicrobial capacity of some phenolic compounds found in these formulations. The results obtained in this study might be a real asset in the choice of the best formulation of artichoke, borututu, and milk thistle, providing detailed information about the chemical composition of the plants and the bioactivity variation associated to the use of the different kinds of formulations, either as single and as combined preparations.