Antioxidant effectiveness as influenced by phenolic content of fresh orange juices.

Several fresh orange juices, obtained from five different Citrus sinensis (L.) Osbeck varieties (three pigmented varieties, Moro, Sanguinello, and Tarocco, and two blond varieties, Valencia late and Washington navel), were subjected to antioxidant profile determination (including total polyphenols, flavanones, anthocyanins, hydroxycinnamic acids, and ascorbic acid). The antioxidant activity of these juices was then assessed by means of different "in vitro" tests (bleaching of the stable 1,1-diphenyl-2-picrylhydrazyl radical; peroxidation, induced by the water-soluble radical initiator 2,2'-azobis(2-amidinopropane) hydrochloride, on mixed dipalmitoylphosphatidylcholine/linoleic acid unilamellar vesicles; scavenging activity against nitric oxide; total antioxidant status). All orange juices tested showed an evident antioxidant effect. Our findings indicate the following: (1) the antioxidant efficiency of orange juices may be attributed, in a significant part at least, to their content of total phenols, (2) while ascorbic acid seems to play a minor role; (3) the antioxidant activity of orange juices is related not only to structural features of phytochemicals contained in them, but also to their capability to interact with biomembranes; (4) finally, as to pigmented juices, their antioxidant efficiency appears to be widely influenced by the anthocyanin level. One could speculate that the supply of natural antioxidant phenols through daily consumption of orange juice might provide additional protection against in vivo oxidation of cellular biomolecules.

On the in-vitro antimicrobial activity of oleuropein and hydroxytyrosol.

Secoiridoides (oleuropein and derivatives), one of the major classes of polyphenol contained in olives and olive oil, have recently been shown to inhibit or delay the rate of growth of a range of bacteria and microfungi but there are no data in the literature concerning the possible employment of these secoiridoides as antimicrobial agents against pathogenic bacteria in man. In this study five ATCC standard bacterial strains (Haemophilus influenzae ATCC 9006, Moraxella catarrhalis ATCC 8176, Salmonella typhi ATCC 6539, Vibrio parahaemolyticus ATCC 17802 and Staphylococcus aureus ATCC 25923) and 44 fresh clinical isolates (Haemophilus influenzae, eight strains, Moraxella catarrhalis, six strains, Salmonella species, 15 strains, Vibrio cholerae, one strain, Vibrio alginolyticus, two strains, Vibrio parahaemolyticus, one strain, Staphylococcus aureus, five penicillin-susceptible strains and six penicillin-resistant strains), causal agents of intestinal or respiratory tract infections in man, were tested for in-vitro susceptibility to two olive (Olea europaea) secoiridoides, oleuropein (the bitter principle of olives) and hydroxytyrosol (derived from oleuropein by enzymatic hydrolysis and responsible for the high stability of olive oil). The minimum inhibitory concentrations (MICs) calculated in our study are evidence of the broad antimicrobial activity of hydroxytyrosol against these bacterial strains (MIC values between 0.24 and 7.85 microg mL(-1) for ATCC strains and between 0.97 and 31.25 microg mL(-1) for clinically isolated strains). Furthermore oleuropein also inhibited (although to a much lesser extent) the growth of several bacterial strains (MIC values between 62.5 and 500 microg mL(-1) for ATCC strains and between 31.25 and 250 microg mL(-1) for clinical isolates); oleuropein was ineffective against Haemophilus influenzae and Moraxella catarrhalis. These data indicate that in addition to the potential employment of its active principles as food additives or in integrated pest-management programs, Olea europaea can be considered a potential source of promising antimicrobial agents for treatment of intestinal or respiratory tract infections in man.

In vitro antioxidant activity and in vivo photoprotective effect of a red orange extract.

Ultraviolet radiation causes damage to the skin, which may result in both precancerous and cancerous skinlesions and acceleration of skin ageing. Topical administration of enzymatic and non-enzymatic antioxidants is an effective strategy for protecting the skin against UV-mediated oxidative damage. Hence, a systematic study to evaluate the in vitro antioxidant activity and in vivo photoprotective effect of a standardized red orange extract (ROE) has been undertaken, where the main active ingredients are anthocyanins, hydroxycinnamic acids, flavanones and ascorbic acid. For the in vitro experiments, the ROE was tested in three models: (1) bleaching of the stable 1,1-diphenyl-2-picrylhydrazyl radical (DPPH test); (2) peroxidation, induced by the water-soluble radical initiator 2,2'-azobis(2-amidinopropane) hydrochloride, of mixed dipalmitoylphosphatidylcholine/linoleic acid unilamellar vesicles (LUVs) (LP-LUV test); and (3) UV-induced peroxidation of phospatidylcholine multilamellar vesicles (UV-IP test). The in vivo antioxidant/radical scavenger activity was assessed by determining the ability of topically applied ROE to reduce UVB-induced skin erythema in healthy human volunteers. The results obtained in the DPPH, LP-LUV and UV-IP tests demonstrated the strong antioxidant properties of ROE, with a clear relationship between ROE scavenger efficiency and its content in antioxidant compounds. In particular, the findings obtained in the UV-IP test provide a strong rationale for using this extract as a photoprotective agent. During in vivo experiments, ROE provided to efficiently protect against photooxidative skin damage when topically applied immediately after skin exposure to UVB radiations. Interestingly, the protective effect of ROE appears higher than that elicited by another natural antioxidant (tocopherol) commonly employed in cosmetic formulations. In conclusion, the present findings demonstrate that ROE affords excellent skin photoprotection, which is very likely a result of the antioxidant/radical scavenger activity of its active ingredients. Thus, ROE might have interesting applications in both anti-photoageing and after-sun cosmetic products.