Extraction and evaluation of glucosinolates from broccoli (Brassica oleracea) seeds and the scale-up evaluation for industrial production

Abstract

Broccoli (Brassica oleracea L., var. italica) is a popular vegetable with unique nutritional characteristics. During the last decade, the consumption of broccoli increased since it has shown great potential to prevent and treat different chronic- degenerative diseases. These characteristics are mainly due to glucosinolates (sulfur-containing glycosides) and their enzymatic degradation metabolites (isothiocyanates). Despite all these beneficial effects, glucosinolates have shown low stability during digestive process, absorbing just a little part of the fraction consumed. Moreover, due to the properties of glucosinolates against chronic diseases, dietary supplements rich in these compounds have been developed. The objective of this study was to evaluate different bioprocess conditions for the extraction of glucosinolates from broccoli (brassica oleracea) and use the extracted compounds for the formulation of a dietary supplement. The first study evaluated combinations of temperature (15, 25, 40, 55, 64 oC), ethanol-water concentration (0, 25, 50, 75, 100%), and sample:solvent ratio (1:15, 1:20, 1:25, 1:30, 1:35 w/v) on the extraction of glucosinolates from broccoli sprouts. Glucosinolates were analyzed by high performance liquid chromatography coupled to photodiode array detector (HPLC-DAD). The treatment with 40oC, 50% ethanol/water (v/v), 1:35 (w/v) in broccoli sprouts generated the highest extraction of total glucosinolates (100,094 ± 9016 mg/kg 6 DW). Results indicated that ethanol percentage was the factor that had the greatest impact on glucosinolate extraction (p<0.05). In the second study, the aim was to obtain an extract rich in glucosinolates from broccoli seeds using the optimal conditions obtained from the first study. The extract was incorporated into a capsule formulation and further characterization of the capsule using in vitro digestion techniques and stability test. Results indicated that the total glucosinolate concentration was 66,874 mg/kg DW for broccoli seed extract and 33,818 mg/kg DW for the formulated powder. Furthermore, the in vitro digestion was performed comparing dried seeds, extract from broccoli seeds and the formulated capsule. Loses in all levels of individual and total glucosinolates were found, considering the fractions submitted to digestion., finding that the formulated capsule was the one that showed the highest final glucosinolate concentration for all the identified compounds. Furthermore, stability test was carried out using the formulated capsule, at 25 and 40oC for thirty days. Results showed that there were not significant changes in contents of the bioactives when compared with the initial time (p<0.05). With the results obtained in the present study, it is suggested to extract phytochemicals from the seed compared instead of sprouts at an industrial level. In addition, it was observed that germination reduces the amount of glucoraphanin in the final extract. Finally, it was possible to obtain extracts rich in glucosinolates ready for the scalability process and preparation of dietary supplements with possible application in the prevention and treatment of chronic- degenerative diseases.