Triterpenoid saponins are a class of plant secondary metabolites with structure derived from the precursor oxidosqualene in which one or more sugar residues are added. They have a wide range of pharmacological applications, such as antiplatelet, hypocholesterolemic, antitumoral, anti-HIV, immunoadjuvant, anti-inflammatory, antibacterial, insecticide, fungicide and anti-leishmanial agents. Their accumulation in plant cells is stimulated in response to changes mediated by biotic and abiotic elicitors. The enhancement of saponin yields by methyl jasmonate in plants and cell cultures in several species indicates the involvement of these metabolites in plant defence mechanisms. The elucidation of their biosynthesis at the molecular level has advanced recently. Most studies to date have focused on the participation of early enzymes in the pathway, including oxidosqualene cyclase, squalene synthase and dammarenediol synthase, as well as in isolating and characterizing genes that encode beta-amyrin synthase. Yields of bioactive saponins in various plant species and experimental systems have been successfully increased by treating cells and tissues with jasmonate or by exposing these to oxidative stress. These elicitation and molecular studies are consolidating a robust knowledge platform from which to launch the development of improved sources for commercial supply of bioactive saponins.

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Plant secondary metabolism evolved in the context of highly organized and differentiated cells and tissues, featuring massive chemical complexity operating under tight environmental, developmental and genetic control. Biotechnological demand for natural products has been continuously increasing because of their significant value and new applications, mainly as pharmaceuticals. Aseptic production systems of plant secondary metabolites have improved considerably, constituting an attractive tool for increased, stable and large-scale supply of valuable molecules. Surprisingly, to date, only a few examples including taxol, shikonin, berberine and artemisinin have emerged as success cases of commercial production using this strategy. The present review focuses on the main characteristics of plant specialized metabolism and their implications for current strategies used to produce secondary compounds in axenic cultivation systems. The search for consonance between plant secondary metabolism unique features and various in vitro culture systems, including cell, tissue, organ, and engineered cultures, as well as heterologous expression in microbial platforms, is discussed. Data to date strongly suggest that attaining full potential of these biotechnology production strategies requires being able to take advantage of plant specialized metabolism singularities for improved target molecule yields and for bypassing inherent difficulties in its rational manipulation.

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A good correlation was obtained between the antioxidant activities of Cannabis sativa samples determined by spectrophotometric and electrochemical methods.

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Saponin-based adjuvants are promising adjuvants that enhance both humoral and T-cell-mediated immunity. One of the most used natural products as vaccine adjuvants are Quillaja saponaria bark saponins and its fraction named Quil A®. Despite that, its use has been restricted for human use due to safety issues. As an alternative, our group has been studying the congener species Quillaja brasiliensis saponins and its performance as vaccine adjuvants, which have shown to trigger humoral and cellular immune responses comparable to Quil A® but with milder side effects. Here, we studied a semi purified aqueous extract (AE) and a previously little characterized saponin-enriched fraction (QB-80) from Q. brasiliensis as vaccine adjuvants and an inactivated virus (bovine viral diarrhea virus, BVDV) antigen co-formulated in experimental vaccines in mice model. For the first time, we show the spectra pattern of the Q. brasiliensis saponins by MALDI-TOF, a novel and cost-effective method that could be used to characterize different batches during saponins production. Both AE and QB-80 exhibited noteworthy chemical similarities to Quil A®. In addition, the haemolytic activity and toxicity were assessed, showing that both AE and QB-80 were less toxic than Quil A®. When subcutaneously inoculated in mice, both fractions promoted long-term strong antibody responses encompassing specific IgG1 and IgG2a, enhanced the avidity of IgG antibodies, induced a robust DTH reaction and significantly increased IFN-ɣ production in T CD4 and T CD8 cells. Furthermore, we have proven herein that AE has the potential to promote dose-sparing, substantially reducing the dose of antigen required for the BVDV vaccines and still eliciting a mixed Th1/Th2 strong immune response. Based on these results, and considering that AE is a raw extract, easier and cheaper to produce than commercially available saponins, this product can be considered as candidate to be escalated from experimental to industrial uses.

In this study, a preparation of saponins (QB-90U) extracted from leaves of Quillaja brasiliensis collected in Uruguay was evaluated as a vaccine adjuvant by comparison with alum and the well known saponin-based adjuvant, Quil A. The haemolytic activity and cellular toxicity of the saponin preparations were also evaluated. QB-90U was only slightly haemolytic and showed a low cytotoxicity when compared to Quil A. The adjuvant properties of QB-90U were assayed by sub-cutaneous immunization of mice with a preparation of inactivated bovine herpesvirus 5 (BoHV-5) either with no adjuvant or adjuvanted with QB-90U, Quil A or alum. Serum levels of anti-BoHV-5 IgG, IgG1, IgG2a, IgG2b and also IgG3 were significantly increased by QB-90U and were of the same order as those elicited by Quil A. Furthermore, high titres of neutralizing antibodies were found to be present in the serum of immunized animals from both groups. The cellular response induced by QB-90U did also reproduce the one elicited by Quil A. In fact, a robust DTH response was observed in mice immunized with both saponin preparations; as well as increased splenocytes levels of Th1-type cytokines, namely IFN-γ and IL-2. Taken together, the above results confirm and extend our previous observation regarding the similarity of the responses elicited by Quil A and the saponin preparation from Q. brasiliensis (Fleck et al., 2006) and indicate that QB-90U is worth of further studies as a safe and potent vaccine adjuvant.