Biologically Active Phenolic Compounds in Fruits and Leaves of Cyclanthera pedata (L.) Schrab (caigua) and in related plant-derived Food Supplements

Cyclanthera pedata (L.) Schrad., known as caigua, is an edible plant belonging to the Cucurbitaceae family and native to South America, which is also used for therapeutic purposes. The local folk medicine recommends the daily intake of fruits and leaves of caigua for the treatment of several diseases, e.g. diabetes, high blood pressure and LDL-cholesterol. Recently, food supplements produced from caigua fruits are available on the European market. They would be associated with anti-hypercholesterolemic and anti-hypertensive properties, also reported in literature. Recent scientific studies relate the anti-hyperglycaemic properties of this plant to the high content of phenolic compounds, the most abundant class of secondary metabolites, and in particular to the glycosylated flavonoids' subclass. Currently, high performance liquid chromatography (HPLC) is the technique of choice for the qualitative and quantitative analysis of phenolic compounds extracted from caigua. Nevertheless, high performance thin layer chromatography (HPTLC) is widely employed for the initial examination of plant extracts before HPLC analysis, because of well-known advantages, such as short separation times, amenable to detection reagents, possibility of running several samples simultaneously, and suitability to be hyphenated to mass spectrometry (HPTLC-MS). The aim of this work has been to investigate the occurrence and content of phenolic compounds in a commercial food supplement in comparison to those determined in leaves and fruits of caigua. As part of the research, an HPTLC-MS method was developed for the preliminary screening of phenolic compounds occurring in the above samples. Further studies were performed in order to investigate the influence of pedo-climatic conditions and vegetative state on the accumulation of phenolic compounds in the leaves and fruits of plants grown in different geographical areas, with the purpose to select the best growth conditions to get raw materials with a greater amount of beneficial molecules for food supplements manufacture. More in-depth analysis were performed by developing an HPLC-MS method and the resulting data were compared with previously obtained results. A total of ten glycosylated flavonoids were identified, nine of which already reported in literature, while one was never identified before. Both HPLC and HPTLC data converge in hypothesizing a strong influence of plant vegetative state on the accumulation of phenolic compounds in caigua leaves, while both techniques reveal the presence of more preserved phenolic patterns in the caigua fruits. Moreover, a simple hydrolysis procedure, having the advantages of miniaturisation (low sample and solvent consumption), simultaneous hydrolysis of multiple samples, use of inexpense glassware, and no need of instrumentation, was developed, in order to confirm the phenolics characterization in the studied plant. The redox activity and the levels of vitamin C in leaves and fruits of C. pedata were determined as well. All obtained results are reported and discussed in this thesis.