Lošić et al. 2020, Biologica Nyssana 11(1) 11 (1) September 2020: 55-58 DOI: 10.5281/zenodo.4060300 Total phenol content and antioxidant potential of different Brassica oleracea varieties Original Article Ajna Lošić Laboratory for Plant physiology, Faculty of Sci- ence, University of Sarajevo, Sarajevo, Bosnia and Herzegovina ajna.losic@gmail.com Adisa Parić Laboratory for Plant physiology, Faculty of Sci- ence, University of Sarajevo, Sarajevo, Bosnia and Herzegovina adisacausevic@hotmail.com Arnela Demir Laboratory for Plant physiology, Faculty of Sci- ence, University of Sarajevo, Sarajevo, Bosnia and Herzegovina arnela_s1@yahoo.com Erna Karalija Laboratory for Plant physiology, Faculty of Sci- ence, University of Sarajevo, Sarajevo, Bosnia and Herzegovina erna.karalija@gmail.com (corresponding author) Received: February 20, 2020 Revised: March 24, 2020 Accepted: March 28, 2020 Abstract: Varieties of Brassica oleracea are commonly used in human nutrition. Beside nutritive role it is suggested that diets reach in cabbage play important role in disease prevention. The aim of this study was to determine total phenol content and the antioxidant potential of different Brassica oleracea varieties (broccoli, brussel sprouts, cauliflower, green cabbage and red cabbage). The highest content of total phenols was found in red cabbage and the lowest in broccoli. Red cabbage had the highest ability to remove free radicals, while the lowest radical scavenging activity was recorded for broccoli. Strong correlation between phenolic content and antioxidant activity suggests the importance of phenolics in health benefits of cabbages. The study identified differences between different varieties suggesting different nutritional advantages, providing useful information in selection of right cabbage variety as diet supplement in disease prevention. Key words: Brussel sprouts, Broccoli, cauliflower, DPPH radical scavenging, green cabbage, phenols, red cabbage Apstract: Ukupan sadržaj fenola i antioksidativni potencijal različitih varijeteta Brassica oleracea Različiti varijeteti vrste Brassica oleracea često se koriste u ishrani ljudi. Pored hranljive uloge, smatra se da ishrana bogata kupusom ima važnu ulogu u prevenciji bolesti. Cilj ovog istraživanja bio je da se utvrdi ukupan sadržaj fenola i antioksidativni potencijal različitih varijeteta vrste Brassica oleracea (brokoli, kelj pupčar, karfiol, zeleni kupus i crveni kupus). Najveći sadržaj ukupnih fenola utvrđen je u crvenom kupusu, a najmanji u brokoliju. Crve- ni kupus je imao najveću sposobnost uklanjanja slobodnih radikala, dok je najmanja aktivnost uklanjanja radikala zabeležena kod brokolija. Izražena korelacija između sadržaja fenola i antioksidativne aktivnosti ukazuje na značaj fenola u zdravstvenim prednostima kupusa. Studija je identifikovala razlike između različitih varijeteta koje sugerišu različite nutritivne prednosti, pružajući korisne informacije u izboru prave sorte kupusa kao dodatak ishrani u prevenciji bolesti. Ključne reči: kelj pupčar, brokoli, karfiol, DPPH uklanjanje radikala, zeleni kupus, fenoli, crveni kupus Introduction Brassicaceae (Cruciferae) or the cabbage family includes many economically important, edible and industrial types of oilseeds, vegetables, spices and fodder. This family is also known to comprise more than 120 wild species, some of which are very im- portant for agriculture e.g. Sinapsis arvensis and Raphanus sativus (Warwick, 2011). The long history of plant selection has resulted that this crop group is highly variable in use, appearance and phytochemis- try. Brassica oleracea is a good example with sever- al important varieties: broccoli, cauliflower, Brussel sprouts, cabbage, kale (Bjorkman et al., 2011). Oxidative stress has been identified as a major cause of the development and progression of several diseases. Supplementation with exogenous antioxi- dant or enhancement of endogenous antioxidant de- fence of the body is a promising way of counteract- ing the reactive oxygen species (ROS) side effects that cause oxidative damage. Plants have long been a source of exogenous antioxidants. Two-thirds of © 2020 Lošić et al. This is an open-access article distributed under the terms of the Creative Commons At- tribution License, which permits unrestricted use, distribution, and build upon your work non-commercially under the same license as the original. 55 the worlds’ plant species are thought to be medically significant, and almost all of them have excellent antioxidant potential. Plants have effective, complex enzymatic and non-enzymatic antioxidant defence systems to avoid the toxic effects of free radicals and non-enzymatic antioxidant system including secondary metabolites as antioxidants (Kasote et al., 2015). Phenolic compounds from plants represent the largest group of secondary plant metabolites found in fruits, vegetables and teas. They are character- ized by antioxidant, anti-inflammatory, anticancero- genic and other biological properties, and can pro- tect plants from oxidative stress and some diseases (Ahmed et al., 2017). Over the last few decades, vegetables from the Brassicaceae family have come under scientific at- tention because of numerous epidemiological stud- ies that provide evidence that diets rich in these veg- etables are associated with a reduces risk of several types of cancer and other chronic diseases. Because of that, these vegetables are considered promising sources of metabolites for cancer prevention, and mechanism of anticancerogenic activity is mostly associated with glucosinolate degradation products (Šamec et al., 2019). The aim of this study was to determine the content of total phenols and antioxidant potential of selected Brassica oleracea varieties (broccoli, cauliflower, Brussel sprouts, green cabbage, and red cabbage). Material and methods Plant material Five mostly consumed Brassica oleracea varie- ties were selected for the analysis: B. oleracea var. capitata (green cabbage) – fresh leaves; B. olera- cea var. capitata f. rubra (red cabbage, Bosnia and Herzegovina) – fresh leaves; B. oleracea var. italica (broccoli) – broccoli flowers (frozen by rapid freez- ing technique); B. oleracea var. botrytis (cauliflow- er) – fresh flowers of cauliflower; B. oleracea var. gemmifera (Brussel sprouts) – axillary buds were used (frozen by rapid freezing technique). Extract preparation All samples were air-dried and extraction was per- formed by maceration with 80% ethanol. Prepared macerate was incubated in the dark at 4 °C for 24 hours. After incubation, macerate was centrifuged at 5000 rpm for 30 minutes, and supernatant was col- lected for the analysis. Extract yield was determined for all samples. Analysis of total phenol content Analysis of phenol content in ethanol extracts of different B. oleracea varieties was performed using Folin Ciocalteu reagent (FCR), by diluting 20 mL of extract with 1580 mL water and adding 100 mL of FCR, followed by addition of 300 mL 7.5% Na2CO3 after 3 min of incubation (Wolfe et al., 2003). Total phenols were quantified based on the direction of the calibration curve of gallic acid. The obtained values are expressed as mg of gallic acid equivalents per gram of dry material (mg GA/gDW). Analysis of antioxidant capacity The DPPH (2,2 – diphenyl – 1 – picrylhydrazyl) method was used to determine the antioxidant ac- tivity of the tested extracts (Mishra et al., 2012). A stock solution of DPPH was prepared by weighing 50 mg of DPPH and dissolving in 100 mL of 96% ethanol. A working DPPH was prepared by diluting 5 mL of stock solution with 96% ethanol to the 50 mL mark and by adjusting DPPH absorbance read- ing to 1.123 at 517 nm (Lambda 25; Perkin Elmer). Extract testing was performed by mixing 100 mL of extract with diluted DPPH and final absorbance reading was recorded after 30 minutes against 96% ethanol (blank). Free radical scavenging activity was calculated by the formula: AA% - antioxidant capacity; A(t0) – absorbance at 0 seconds; A(60) – absorbance after 60 seconds. Nar- ingenin was used as a standard in concentration of 1 mg/ml. Statistical analysis The data were expressed as means of three inde- pendent replicates ± standard deviation. All data were statistically evaluated by analysis of variance with the ANOVA test (p< 0.05 significance level), and the means were analyzed by regression analysis by Newman Keuls test. Pearson’s correlation was used to assess relationships between the variables. All statistical testing was performed using STATIS- TICA 10 software (Copyright© StatSoft, Inc. 1984- 2011). Results and Discussion Differences in extract yield for different B. oleracea cultivars were recorded. The highest yield was noted for green cabbage (21.5%), followed by red cab- bage, cauliflower and sprouts, and the lowest yield was registered for broccoli (2.6%) (Tab. 1). The dif- ferences in extract yield for the analyzed B. olera- cea varieties can be attributed to the availability of the components that are extracted from the sample, which in itself depends on the analyzed variety (Hsu et al., 2006). Also, the effectiveness of the solvent 56 BIOLOGICA NYSSANA ● 11 (1) September 2020: 55-58 Lošić et al. ● Total phenol content and antioxidant potential of different Brassica oleracea varieties 57 BIOLOGICA NYSSANA ● 11 (1) September 2020: 55-58 Lošić et al. ● Total phenol content and antioxidant potential of different Brassica oleracea varieties used for extraction to dissolve endogenous compo- nents has a significant effect on the yield of the ex- tracts (Siddhuraju & Becker, 2003). Other factors that can affect yield of extract sol- vent polarity, extraction time and temperature as well as the chemical nature of the sample itself (Sun & Ho, 2005). The choice of extraction solvent was selected according to targeted components (pheno- lics). The analysis of total phenolic content showed high concentrations in red cabbage, while broccoli contained only small amounts of phenolics (Tab. 1). Compared to other extraction solvents, 80% ethanol is less effective and methanol extracts are richer in phenolics as previously recorded by Jaiswal et al. (2011). High phenolic content in red cabbage is probably result of high sinapic acid content as pre- viously recorded in other studies (Mattila & Hell- ström, 2007). Analysis of DPPH radical scavenging activity by ethanol extracts of different varieties of B. oleracea are shown in Tab. 1. The antioxidant capacity of the tested extracts ranged from 86.63% to 7.14% for red cabbage and broccoli, respectively. Total phenolic content strongly correlated with DPPH scavenging activity (R2 0,9755; p<0,05). High antioxidant ca- pacity of red cabbage has been previously recorded by several authors (Podsędek et al., 2006; Isabelle et al., 2010; Rokayya et al., 2013; Liang et al., 2019). Miller et al. (2000) studied the antioxidant effects of different vegetables and noticed a striking differ- ence between red and green cabbage, suggesting a strong role of red cabbage pigment in antioxidant activity. Oxidative stress is one of major causes for patho- physiology of several cardiovascular diseases (La- hera et al., 2007). Dietary phenolic antioxidants play significant role in counteracting cardiovascular dis- eases (Chiu et al., 2018) and intake of red cabbage is beneficial for human health, as suggested by our study as well. Conclusion Presented study evaluated different Brassica olera- cea varieties for their phenolic content and antioxi- dative capacity. Among the tested varieties, red cab- bage had the highest phenolic content and significant antioxidant capacity, suggesting the importance of red cabbage in human nutrition. 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BIOLOGICA NYSSANA ● 11 (1) September 2020: 55-58 Lošić et al. ● Total phenol content and antioxidant potential of different Brassica oleracea varieties