Znanstvena dela

Oxidant/antioxidant properties of Croatian native propolis

Sobočanec S, Šverko V, Balog T, Šaric A, Rusak G, Likić S, Kušić B, Katalinić V, Radić S, Marotti T.

Division of Molecular Medicine, Ruder Boskovic Institute, Zagreb.

Native propolis was defined as propolis powder collected from the continental part of Croatia and prepared according to a patented process that preserves all the propolis natural nutritional and organoleptic qualities.

Nine phenolic compounds (out of thirteen tested) in propolis sample were detected by high performance liquid chromatography (HPLC) analysis. Among them chrysin was the most abundant (2478.5 microg/g propolis). Contrary to moderate antioxidant activity of propolis examined in vitro (ferric reduction antioxidant power; FRAP-assay), propolis as a food supplement modulatedantioxidant enzymes (AOE) and significantly decreased lipid peroxidation processes (LPO) in plasma, liver, lungs, and brain of mice. The effect was dose- and tissue-dependent. The lower dose (100 mg/kg bw) protected plasma from oxidation, whereas the higher dose (300 mg/kg bw) was pro-oxidative. Hyperoxia (long-term normobaric 100% oxygen) increased LPO in all three organs tested.

The highest vulnerability to oxidative stress was observed in lungs where hyperoxia was not associated with augmentation of AOE. Propolis protected lungs from hyperoxia by increased catalase (CAT) activity. This is of special importance for lungs since lungs of adult animals are highly vulnerable to oxidative stress because of their inability to augment AOE activity. Because of its strong antioxidant and scavenging abilities, native propolis might be used as a strong plant-based antioxidant effective not only in physiological conditions but also in cases that require prolonged high concentration of oxygen.

Antitumor effect of Croatian propolis as a consequence of diverse sex-related dihydropyrimidine dehydrogenase (DPD) protein expression

Sobočanec S, Balog T, Sariċ A, Mačak-Šafranko Z, Stroser M, Zarković K, Zarković N, Stojković R, Ivanković S, Marotti T.

Division of Molecular Medicine, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia.

The aim of this study was to detect the antitumor properties of Croatian propolis in BALB/c male and female mice injected with 4T1 mammary carcinoma. Furthermore, the gender-dependence of this effect and the possible involvement of combined effect of propolis and 5-Fluorouracil (5FU) on dihydropyrimidine dehydrogenase (DPD) transcriptional and translational level, were determined. In combination with 5FU propolis treatment induced gender-related effects. The results of the study revealed that pretreatment of mice with propolis combined with 5FU treatment prolonged the suppressive effect of 5FU on tumor growth and reduced the number of metastasis only in male mice. Only males pretreated with propolis prior to 5FU administration had decreased DPD protein level indicating higher sensitivity to 5FU. Thus, benefitial effects of propolis in male tumor-bearing mice treated with 5FU might be explained by increased sensitivity to 5FU as the result of translationally downregulated DPD.

* In our study we used propolis in powder prepared with no chemical refinement (an original treatment by firm HEDERA d.o.o., Stobrec, Croatia).

Phytomedicine. 2011 Feb 24. [Epub ahead of print]

Antioxidative activity of propolis from Dalmatia (Croatia)

Katalinić V, Radić S, Ropac D, Mulić R, Katalinić A.

Oddelek sanitarne kemije in toksikologije, Inštitut pomorske medicine HRM, Split, Hrvaška.

AIM: The aim of this study was to determine the antioxidative activity of propolis from ecologically clean parts of Dalmatia.

METHODS: Phenol concentration in ethanolic propolis extracts was determined by Folin-Ciocalteu reagent using gallic acid as the standard. Flavonoid phenolic compounds were analyzed after precipitation with formaldehyde. The residual non-flavonoid phenolics were also determined by Folin-Ciocalteu method. By determining the change of peroxide number (PN), of tiobarbiture acid reactive species (TBARS), and of DPPH-radical activity, antioxidative efficiency of propolis was tested and compared with well known and widely used synthetic antioxidants. Values of PN and TBARS were determined at 60 degrees C in samples of trigyceride substrate (lard) without and with the addition of antioxidants. Compared was the efficiency of three antioxidants: propolis (alcoholic extract), vitamin E, and (+)-catechin in a concentration of 1%. PN was monitored during 50 days. By the method of Sedlacek, TBARS were measured during 30 days. Antioxidative activity of propolis extract was also measured in terms of hydrogen donating ability using stable radical alpha, alpha-diphenyl-beta-picril hidrazyl (DPPH*) and compared with commercial synthetic antioxidants of butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and (+)-cathecin. Inhibition degree of DPPH* was calculated by the formula of Yen and Duh.

RESULTS: Total phenol content, expressed as gallic acid, in propolis extracts varied from 75.2 to 90.2 g/kg propolis. The proportion of flavonoids in total phenols ranged from 62% to 65%. Values of TBARS were not increased only in samples with added propolis. The inhibition of DPPH-radical by propolis extracts ranged from 93% to 96%, by catechin 95%, by BHT 49%, and by BHA 64%. Compared to BHT and BHA, propolis extracts showed greater reducing activity against DPPH-radical.

DISCUSSION: The chemical composition of propolis, and thus its biological activity depend on the plant from which it has been collected, and on the macro- and microclimatic conditions. Many compounds in propolis exert antioxidative activity. A belief was expressed that the biological activity of propolis is very probably based mostly on its antioxidative efficiency. Dalmatian propolis showed high efficiency in the prevention of oxidative processes. This could be explained by the high proportion of polyphenol constituents, especially flavonoids. A very low and equal degree of increase of PN, as a measure of oxidative processes, was noticed in the samples of triglyceride substrate with the addition of propolis and (+)-catechin. The greatest rise of TBARS was measured in the samples of pure lard. There was no increase of TBARS only in the samples with added propolis. Propolis and (+)-catechin showed great efficiency in the inhibition of DPPH-radical, greater than BHT and BHA, which are widely used in food industry.

CONCLUSION: The results indicate that Dalmatian propolis could be an efficient protective agent against oxidative processes in food. The high antioxidative activity of propolis, its natural origin, and present knowledge about its biological properties, make it a very promising nutritional additive for human diet.

Antioxidant effects of flavonoid from Croatian Cystus incanus L. rich bee pollen

Sarić A, Balog T, Sobocanec S, Kusić B, Sverko V, Rusak G, Likić S, Bubalo D, Pinto B, Reali D, Marotti T

Division of Molecular Medicine, Rudjer Bosković Institute, Bijenicka 54, 10000 Zagreb, Croatia.

Oxidant/antioxidant status, estrogenic/anti-estrogenic activity and gene expression profile were studied in mice fed with Cystus incanus L. (Cistaceae) reach bee pollen from location in Central Croatia’s Dalmatia coast and offshore islands. Seven phenolic compounds (out of 13 tested) in bee pollen sample were detected by high performance liquid chromatography (HPLC) analysis. Phenolics detected in C. incanus L. bee pollen belong to flavonol (pinocembrin), flavanols (quercetin, kaempferol, galangin, and isorhamnetin), flavones (chrysin) and phenylpropanoids (caffeic acid). Bee pollen as a food supplement (100mg/kgbw mixed with commercial food pellets) compared to control (commercial food pellets) modulated antioxidant enzymes (AOE) in the mice liver, brain and lysate of erythrocytes and reduced hepatic lipid peroxidation (LPO). Bee pollen induced 25% of anti-estrogenic properties while no estrogenic activity was found. Differential gene expression profile analyses after bee pollen enriched diet identify underexpressed gene Hspa9a, Tnfsf6 (liver) and down-regulated gene expression of Casp 1 and Cc121c (brain) which are important in the apoptosis pathway and chemotaxis. These results indicate that used bee pollen possess a noticable source of compounds with health protective potential and antioxidant activity.

Food Chem Toxicol. 2009 Mar;47(3):547-54. Epub 2008 Dec 16.