Abstract
A wide variety of polyphenols are reported to have considerable antioxidant and skin photoprotective effects, although the mechanisms of action are not fully known. Environmentally friendly and inexpensive sources of natural bioactive compounds, such as olive mill wastewater (OMWW), the by-product of olive-oil processing, can be considered an economic source of bioactive polyphenols, with a range of biological activities, useful as chemotherapeutic or cosmeceutical agents. Green strategies, such as the process based on membrane technologies, allow to recover active polyphenols from this complex matrix. This study aims to evaluate the antioxidant, pro-oxidant, and photoprotective effects, including the underlying action mechanism(s), of the ultra-filtered (UF) OMWW fractions, in order to substantiate their use as natural cosmeceutical ingredient. Six chemically characterized UF-OMWW fractions, from Italian and Greek olive cultivar processing, were investigated for their antioxidant activities, measured by Trolox Equivalent Antioxidant Capacity (TEAC), LDL oxidation inhibition, and ROS-quenching ability in UVA-irradiated HEKa (Human Epidermal Keratinocytes adult) cultures. The photoprotective properties of UF-OMWW were assayed as a pro-oxidant-mediated pro-apoptotic effect on the UVA-damaged HEKa cells, which can be potentially involved in the carcinogenesis process. All the UF-OMWW fractions exerted an effective antioxidant activity in vitro and in cells when administered together with UV-radiation on HEKa. A pro-oxidative and pro-apoptotic effect on the UVA-damaged HEKa cells were observed, suggesting some protective actions of polyphenol fraction on keratinocyte cell cultures.
Highlights
Olive mill wastewater (OMWW) is a polyphenol-rich by-product of olive oil production, representing a major environmental problem in the Mediterranean countries, with an annual OMWW production that ranges between 7 and over 30 million m3 in the productive season [1,2,3]
The OMWW can be efficiently treated by using microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and/or reverse osmosis (RO), and the last permeate fraction can be discharged into aquatic systems in compliance with national and European Union (EU) regulations or be safely used for irrigation
In order to evaluate the OMWW fractions as a source of polyphenols, UF fractions coming from processed Greek and Italian olive cultivars were assayed for total phenol content by the Folin-Ciocalteu method (Figure 1)
Summary
Olive mill wastewater (OMWW) is a polyphenol-rich by-product of olive oil production, representing a major environmental problem in the Mediterranean countries, with an annual OMWW production that ranges between 7 and over 30 million m3 in the productive season [1,2,3]. OMWW has been regarded as a hazardous waste with negative impact on the environment for its high organic load, mainly represented by the polyphenols and other organic molecules, such as lipids, sugars, fibers, and by inorganic compounds, such as metals [4,5] This view has changed, and the OMWW are considered as a potential low-cost row material rich in bioactive compounds, phenolics [6], for which concentrations range from 0.002 to 11.5 g/L [5]. They can be recovered by a green process based on the membrane technologies reducing the organic load [7,8]. They can be used as fertilizers or in the production of biogas in anaerobic reactors [8]
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