Antonio Tomaino

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 vitro and in vivo evaluation of caffeic and ferulic acids as topical photoprotective agents

Topically-applied antioxidant drugs represent a successful strategy for protecting the skin against UV-mediated oxidative damage. However, they can afford to the skin a satisfactory photoprotection only if able to permeate through the stratum corneum and thus to reach deeper cutaneous layers. Caffeic and ferulic acids, dissolved in saturated aqueous solutions at pH 3 or 7.2, have been tested for their capability to permeate through excised human skin mounted in Franz cells. At both pH values, ferulic and, at a lower degree, caffeic acids appeared able to permeate through the stratum corneum. The known higher lipophilicity of ferulic acid may explain the fact that it permeates through the stratum corneum better than caffeic acid. However, vehicle pH values proved to have no influence on biophenol skin permeation profile; this observed lack of pH effect may reflect the drug higher concentration attainable in saturated solutions at high pH. On the basis of the findings obtained in these in vitro experiments, we designed the schedule of a series of in vivo experiments, carried out to evaluate the ability of caffeic and ferulic acids to reduce, in healthy human volunteers, UVB-induced skin erythema, monitored by means of reflectance spectrophotometry. Caffeic and ferulic acids, dissolved in saturated aqueous solution pH 7.2, proved to afford a significant protection to the skin against UVB-induced erythema. To conclude, we have confirmed, by means of in vitro and in vivo experiments, that caffeic and ferulic acids may be successfully employed as topical protective agents against UV radiation-induced skin damage; however their skin absorption is not influenced by the pH of the formulation.

Flavonoids as potential protective agents against photo-oxidative skin damage

Abstract Flavonoids, a group of phenolic compounds widely occurring in the plant kingdom, have been reported to possess strong antioxidant activity. This preliminary study was designed to estimate the potential utility of topically applied flavonoids to prevent photooxidative stress in the skin. With this aim we have evaluated the protective effect of three flavonoids (quercetin, hesperetin and naringenin), chosen according to their structural characteristics, against UV radiation-induced peroxidation on phosphatidylcholine (PC) vesicles as a model membrane. Furthermore ‘in vitro’ human skin permeation of these flavonoids was measured, given that a suitable percutaneous absorption is an essential requirement for satisfactory topically applied photoprotective agents. The flavonoids tested in our study proved to protect efficiently PC liposomes from UV radiation-induced peroxidation, probably by scavenging oxygen free radicals generated by UV irradiations; their antilipoperoxidative activity can be classified as follows: quercetin > hesperetin > naringenin. In addition, naringenin, hesperetin and, at a very lower degree, quercetin were able to permeate through the stratum corneum (which is the main barrier against the penetration of exogenous substances through the skin) and, so, to penetrate into deeper skin layers. Taken together, these findings suggest that topically applied flavonoids could be excellent candidates for successful employment as protective agents in certain skin diseases caused, initiated or exacerbated by sunlight irradiation.

`In vitro' evaluation of the antioxidant activity and biomembrane interaction of the plant phenols oleuropein and hydroxytyrosol

Abstract Oleuropein and hydroxytyrosol, two phenolic compounds contained in olives and olive oil, are known to possess several biological properties, many of which may be related, partially at least, to their antioxidant and free radical-scavenger ability. Hence, together with their scavenging activity against the stable 1,1-diphenyl-2-picrylhydrazyl radical (DPPH test), we have investigated the antioxidative effect of oleuropein and hydroxytyrosol in a model system consisting of dipalmitoylphosphatidylcholine/linoleic acid unilamellar vesicles (DPPC/LA LUVs) and a water-soluble azo compound as a free radical generator (LP–LUV test). The results obtained were also interpreted in the light of biophenol interactions, studied by differential scanning calorimetry (DSC), with dimyristoylphosphatidylcholine (DMPC) vesicles as a biological membrane model. Our results obtained in the DPPH and LP–LUV tests confirm the good scavenger activity and antioxidant effect of oleuropein and hydroxytyrosol. However, while both compounds exhibit comparable effectiveness in the DPPH test (hydroxytyrosol being slightly more active than oleuropein), oleuropein seems, in the LP–LUV test, a better antioxidant than hydroxytyrosol. Besides oleuropein shows a better antioxidant activity in the membranous system than in homogenous solution. Furthermore, oleuropein, but not hydroxytyrosol, interacts with DMPC vesicles, causing shifts, toward lower values, of the calorimetric peak temperature ( T m ), associated to the gel to liquid-crystal phase transition, typical for DMPC multilayers. The hypothesis will be discussed that hydroxytyrosol can serve as scavenger of aqueous peroxyl radicals near the membrane surface, while oleuropein acts also as a scavenger of chain-propagating lipid peroxyl radicals within the membranes.

Ferulic and caffeic acids as potential protective agents against photooxidative skin damage

The biological properties and, particularly, the antioxidant activity of plant hydroxycinnamic acids, such as caffeic and ferulic acids, are well recognised. This preliminary study was designed to estimate the potential utility of caffeic and ferulic acids to prevent, when topically applied, photooxidative stress in the skin. With this aim we have evaluated the antioxidant activity of ferulic and caffeic acids in two experimental models: (1) the UV radiation-induced peroxidation in phosphatidylcholine (PC) liposomal membranes; (2) the scavenging activity against nitric oxide (a radical involved in oxidative reactions). In addition, given that a suitable percutaneous absorption is an essential requirement for successful topical photoprotective agents, we measured their in vitro permeation through excised human skin. Caffeic and ferulic acids efficiently protected PC liposomes from UV radiation-induced peroxidation and reacted with nitrogen oxides. In addition, caffeic and ferulic acids were able to permeate through the stratum corneum (the main barrier against the penetration of exogenous substances through the skin). Taken together, these findings suggest that caffeic and ferulic acids should be good canditates for successful employment as topical protective agents against UV radiation-induced skin damage. © 1999 Society of Chemical Industry

Antioxidant activity and phenolic profile of pistachio (Pistacia vera L., variety Bronte) seeds and skins

Pistachio (Pistacia vera L.; Anacardiaceae) is native of aride zones of Central and West Asia and distributed throughout the Mediterranean basin. In Italy, a pistachio cultivar of high quality is typical of Bronte (Sicily), an area around the Etna volcano, where the lava land and climate allow the production of a nut with intense green colour and aromatic taste, very appreciated in international markets. Pistachio nuts are a rich source of phenolic compounds, and have recently been ranked among the first 50 food products highest in antioxidant potential. Pistachio nuts are often used after removing the skin, which thus represents a significant by-product of pistachio industrial processing. The present study was carried out to better characterize the phenolic composition and the antioxidant activity of Bronte pistachios, with the particular aim to evaluate the differences between pistachio seeds and skins. The total content of phenolic compounds in pistachios was shown to be significantly higher in skins than in seeds. By HPLC analysis, gallic acid, catechin, eriodictyol-7-O-glucoside, naringenin-7-O-neohesperidoside, quercetin-3-O-rutinoside and eriodictyol were found both in pistachio seeds than in skins; furthermore, genistein-7-O-glucoside, genistein, daidzein and apigenin appeared to be present only in pistachio seeds, while epicatechin, quercetin, naringenin, luteolin, kaempferol, cyanidin-3-O-galactoside and cyanidin-3-O-glucoside are contained only in pistachio skins. The antioxidant activity of pistachio seeds and skins were determined by means of four different assays (DPPH assay, Folin-Ciocalteau colorimetric method and TEAC assay, SOD-mimetic assay). As expected on the basis of the chemical analyses, pistachio skins have shown to possess a better activity with respect to seeds in all tests. The excellent antioxidant activity of pistachio skins can be explained by its higher content of antioxidant phenolic compounds. By HPLC-TLC analysis, gallic acid, catechin, cyanidin-3-O-galactoside, eriodictyol-7-O-glucoside and epicatechin appeared to be responsible for the antioxidant activity of pistachio skin, together with other unidentified compounds. In conclusion, our work has contributed to clarify some particular characteristics of Bronte pistachios and the specific antioxidant power of pistachio skins. Introduction of pistachios in daily diet may be of undoubted utility to protect human health and well-being against cancer, inflammatory diseases, cardiovascular pathologies and, more generally, pathological conditions related to free radical overproduction. On the other hand, pistachio skins could be successfully employed in food, cosmetic and pharmaceutical industry.

Influence of different penetration enhancers on in vitro skin permeation and in vivo photoprotective effect of flavonoids

In the present study the permeation of two flavonoids (naringenin and hesperetin) through excised human skin mounted in Franz diffusion cells and its possible optimization following skin pretreatment with two penetration enhancers (D-limonene and lecithin) were determined. Hesperetin and naringenin were able to permeate through excised human skin; moreover, skin pretreatment with D-limonene and lecithin increased, to different degrees, their cutaneous permeation. On the basis of findings obtained in these in vitro experiments, we designed a schedule for a series of in vivo experiments, in which the protective effect of topically applied naringenin and hesperetin against UV-B-induced skin damage was assessed monitoring the extent of erythema in human volunteers by means of reflectance spectrophotometry. Hesperetin and naringenin from formulations containing the flavonoid alone were completely ineffective in decreasing UV-B-induced erythema. Furthermore, both D-limonene and lecithin have enhanced, to a significant extent, the photoprotective activity of naringenin and hesperetin. Taken together, these data demonstrate that hesperetin and naringenin may be successfully employed as topical photoprotective agents. However their topical activity needs to be optimized by using suitable penetration enhancers.

Antimicrobial potential of polyphenols extracted from almond skins.

Aims:  To evaluate the antimicrobial properties of flavonoid‐rich fractions derived from natural and blanched almond skins, the latter being a by‐product from the almond processing industry.

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.

Flavonoid-biomembrane interactions: A calorimetric study on dipalmitoylphosphatidylcholine vesicles

Flavonoids, a group of naturally occurring benzo-γ-derivatives, have been shown to possess several biological properties, many of which may be related, partially at least, to their capacity to penetrate into the cell membrane and so to affect membrane-dependent processes. In the present paper we report the results of an investigation by differential scanning calorimetry (DSC) on the effects of three flavonoids (quercetin, hesperetin and naringenin) upon the gel-to-liquid crystalline phase transition of model membranes constituted by l-α-dipalmitoylphosphatidylcholine (DPPC) vesicles. All tested flavonoids interacted with DPPC liposomes causing different shifts, towards lower values, of the Tm typical for DPPC multilayers; the enthalpy changes (AH), related to the calorimetric peak area, remained nearly constant. Furthermore, their effects on DPPC thermotropic behaviour were greater for high molar concentrations (up to a limit value different for each flavonoid) and were affected by the time. Several hypotheses (drug molecule aggregation into the model membrane, changes in the barrier function of the lipid bilayer, different drug structural features and conformation, possible formation of flavonoid-phospholipid complexes) are presented to explain the nature of the interaction between flavonoids and phospholipid vesicles.