Bioactive compounds, glucosinolates and poliphenols, within broccoli (Brassica oleracea var. botrytis L.) floret, leaf and stem

Brokula je bogata bioaktivnim spojevima, glukozinolatima i polifenolima, te se uvelike istražuje radi njihova korisnog djelovanja na ljudsko zdravlje. U svjetskoj literaturi mnogo je više radova o sastavu i udjelima bioaktivnih spojeva u cvatu nego u lišću i stabljici biljke. U ovom radu analizirani su ukupni i pojedinačni glukozinolati, slobodni i vezani polifenolni spojevi te njihov antioksidacijski kapacitet u svim navedenim dijelovima brokule. Za određivanje glukozinolata primijenjena je međunarodna standardna metoda za sjeme uljane repice (ISO 10633-1, 1995). Polifenolni spojevi, vezani i slobodni, analizirani su UV/VIS spektrometrijskom metodom uporabom Folin-Ciocalteau reagensa u ekstraktima pripravljenim različitim metodama ekstrakcije: 70 %-tni metanol, 10 min, 75 ºC; 80 %-tni metanol, 3 h, sobna temperatura; 50 %-tni metanol, 2 h, 90 ºC; 80 %-tni metanol, 80 sec, 200 W. Antioksidacijski kapacitet pripravljenih ekstrakata određen je spektrofluorimetrijskom ORAC-metodom. Utvrđeno je da je količina glukozinolata najveća u listu brokule pri čemu udio indolnih prevladava nad alifatskim spojevima što vrijedi i za cvat. U stabljici je veći udio alifatskih spojeva. Udio polifenolnih spojeva u uzorcima u rasponu je od 9,70-16,11 mg GE g-1 ST u stabljici, od 17,65-31,08 mg GE g-1 ST u cvatu i od 22,27-34,02 mg GE g-1 ST u listu brokule. Veću antioksidacijsku aktivnost pokazuju uzorci s većom koncentracijom polifenola.Broccoli is rich in bioactive compounds, polyphenols and glucosinolates, and as such considered as functional food and great experimental material. Previous scientific attention had mostly been focussed on composition and amounts of phytochemicals in florets rather than leaves and stem. In this research, content of total and individual glucosinolates, free and bound polyphenols and antioxidative capacity were studied in broccoli florets, leaves and stems. The standard international method for rapeseed (ISO 10633-1, 1995) has been used for glucosinolate content determination. Extraction of free and bound polyphenols was performed using several different methods: 70 % methanol, 10 minutes at 75 ºC; 80 % methanol, 3 hours at room temperature; 50 % methanol, 2 hours at 90 ºC; 80 % methanol, 80 secconds at 200 W. Extracts were used for assay according to the Folin-Ciocalteau method. Antioxidant capacity has been measured by the oxygen radical absorbance capacity (ORAC) method. Leaves showed to be the most abundant in glucosinolates with indolyl predominating aliphatic as was also the case in florets. In contrast, stem contained more aliphatic than indolyl glucosinolates. Polyphenol quantity ranged from 9.70-16.11 mg GE g-1 DW in stems, from 17.65-31.08 mg GE g-1 DW in florets and from 22.27-34.02 mg GE g-1 DW in leaves and was the highest in leaves irrespective of extraction method. It was determined that samples containing the highest amounts of polyphenols also had the highest antioxidant activity