Hassan K. Obied

Biosynthesis and biotransformations of phenol-conjugated oleosidic secoiridoids from Olea europaea L.

The genus Olea contains the economically important European olive tree (Olea europaea L.). This species is also of chemotaxonomic interest because of the presence of various phenol-conjugated oleosidic secoiridoids or oleosides. The chemistry of these phenolic oleosides is diverse and complicated, and it is only in recent years that attention has been given to their biosynthesis and the biotransformations during the processing and storage of olive products. Many questions regarding these processes remain unanswered, and yet these have significant impact on the quality and value of olive products such as olive oil.

Effect of Processing Conditions, Prestorage Treatment, and Storage Conditions on the Phenol Content and Antioxidant Activity of Olive Mill Waste

The impact of two- and three-phase processing systems and malaxation conditions on phenol content (both total and individual phenols) and antioxidant capacity of laboratory-generated olive mill waste (OMW) was assessed. Two-phase olive processing generated a waste with higher phenol content and antioxidant capacity. Using the two-phase system, both malaxation time and temperature affected the phenol content and antioxidant capacity. The effects of different prestorage drying treatments on phenol content and antioxidant capacity were also compared. Air drying and drying at 60 degrees C resulted in a substantial decrease in the phenol content and antioxidant capacity. Drying at 105 degrees C and freeze-drying produced less degradation. The phenol content and antioxidant capacity of OMW stored at 4 degrees C and of OMW preserved by 40% w/w ethanol and 1% w/w acetic acid and stored at 4 degrees C were monitored for 30 days and compared with those of OMW stored at room temperature. None of these storage conditions could prevent the rapid decrease in phenolic concentrations and antioxidant capacity, which happened within the first 24 h.

Pharmacology of Olive Biophenols

Abstract There are more than 100 different biophenols reported in olive samples. This chapter covers the chemistry, pharmacodynamics, pharmacokinetics, posology, adverse effects, and potential drug interactions of olives and major olive biophenols (OBP). Major biophenols detected in olive samples include hydroxytyrosol, tyrosol and their secoiridoid derivatives (oleuropein, oleuropein aglycone, and elenolic acid dialdehydes), verbascoside, lignans, and flavonoids. By far the majority of reports on the chemistry of OBP pertain to their ability to function as antioxidants, but other bioactivities include binding to lipids, proteins, carbohydrates, and nucleic acids. The majority of pharmacological studies have focused on just four compounds hydroxytyrosol, tyrosol, oleuropein, and verbascoside. Reported pharmacological properties include antioxidant, anti-inflammatory, cardiovascular, immunomodulatory, gastrointestinal, respiratory, autonomic, central nervous system, antimicrobial, anticancer and chemopreventive. While OBP are generally regarded as safe, further studies on potential adverse reactions may be required to demonstrate the safety of supplements with elevated levels of compounds.

Impact of cultivar, harvesting time, and seasonal variation on the content of biophenols in olive mill waste.

Olive mill waste (OMW) contains substantial amounts of valuable antioxidant biophenols that can be recovered for possible applications in food, pharmaceutical, and cosmetic industries. However, the impact of cultivar, harvesting time, and seasonal variation on the phenolic composition of OMW has not yet been assessed. Total phenols, antioxidant activity, and phenol profiles of OMW extracts from five different Australian-grown cultivars (Barnea, Correggiola, Manzanillo, Mission, and Paragon) were studied at four different harvesting times in the 2004 season. The impact of seasonal variation was assessed by comparing total phenol content, antioxidant activity, and phenol profile of two cultivars (Correggiola and Mission) harvested in the 2004 and 2005 seasons. The phenol content and antioxidant activity at different harvesting times were mainly a function of the olive cultivar. Harvesting time had a quantitative effect rather than a qualitative effect on the phenol profile. Intercultivar and harvesting time variation accounted for a 2-5-fold change in the total phenol and antioxidant capacity, while levels of individual biophenols experienced up to 50-fold change. The phenol content and antioxidant capacity of OMW significantly changed between seasons with different variation patterns for different cultivars.

Bioprospecting traditional Pakistani medicinal plants for potent antioxidants.

Antioxidant potential of four methanol extracts from three selected plant species, namely Salvia nubicola (Lamiaceae), Acer oblongifolium (Aceraceae) and Hedera nepalensis (Araliaceae) was measured using assays in aqueous and lipid systems. Antioxidant activities were investigated in aqueous systems by using DPPH radical-scavenging assay, ABTS radical-scavenging assay and DNA protection assay, while antioxidant activity in a lipid system was determined by using the thiobarbituric acid-reactive substances (TBARS) assay. Additionally, the Folin-Ciocalteu method was used to measure total phenolic content. Methanol extracts of leaves and flowers of S. nubicola showed the highest Trolox equivalent (TE) values in the case of the DPPH assay, 2484±4.9mmol TE/g extract, as well as total phenolic content, 139±0.2mg gallic acid equivalents/g extract. Three fractions (A-C) of the methanol extract of S. nubicola leaves and flowers were produced by semi-preparative HPLC. Fraction B was found to be the most active in the DPPH radical-scavenging assay and had the highest total phenol content. HPLC-DAD and LC-MS revealed rosmarinic acid in S. nubicola extracts and chlorogenic acid and rutin in H. nepalensis extracts as the main phenolic antioxidants.

The protective role of plant biophenols in mechanisms of Alzheimer's disease.

Self-assembly of amyloid beta peptide (Aβ) into the neurotoxic oligomers followed by fibrillar aggregates is a defining characteristic of Alzheimers disease (AD). Several lines of proposed hypotheses have suggested the mechanism of AD pathology, though the exact pathophysiological mechanism is not yet elucidated. The poor understanding of AD and multitude of adverse responses reported from the current synthetic drugs are the leading cause of failure in the drug development to treat or halt the progression of AD and mandate the search for safer and more efficient alternatives. A number of natural compounds have shown the ability to prevent the formation of the toxic oligomers and disrupt the aggregates, thus attracted much attention. Referable to the abundancy and multitude of pharmacological activities of the plant active constituents, biophenols that distinguish them from the other phytochemicals as a natural weapon against the neurodegenerative disorders. This review provides a critical assessment of the current literature on in vitro and in vivo mechanistic activities of biophenols associated with the prevention and treatment of AD. We have contended the need for more comprehensive approaches to evaluate the anti-AD activity of biophenols at various pathologic levels and to assess the current evidences. Consequently, we highlighted the various problems and challenges confronting the AD research, and offer recommendations for future research.

Biophenols and antioxidant properties of Australian canola meal.

During the extraction of canola oil, large quantities of meal are produced. Extracting biophenols from Australian canola meal (ACM) adds value to an otherwise low-value agro-industrial byproduct. This study examined the biophenol content and the antioxidant activity of ACM, the impact of extraction conditions, and varietal differences. Sinapine was the principal biophenol in ACM. In crude and hydrolyzed extracts, 31 compounds were identified: 2 dihexosides, 2 organic acids, 4 glucosinolates, 17 sinapic acid derivatives, 2 cyclic spermidine alkaloids, caffeic acid and its dihexoside, kaempferol, and its C-glucoside. ACM showed significant free radical scavenging activity in DPPH(•) and ABTS(•+) assays. Sinapine was the chief contributor to ACM antioxidant activity, whereas kaempferol sinapoyl triglucoside isomer was the most potent antioxidant. Biophenol content ranged between 12.8 and 15.4 mg GAE/g DW. Differences among studied cultivars were generally quantitative. The Tarcoola cultivar showed the highest biophenol content and antioxidant activity.

Plant Phenols as Antibiotic Boosters: In Vitro Interaction of Olive Leaf Phenols with Ampicillin

The antimicrobial properties of olive leaf extract (OLE) have been well recognized in the Mediterranean traditional medicine. Few studies have investigated the antimicrobial properties of OLE. In this preliminary study, commercial OLE and its major phenolic secondary metabolites were evaluated in vitro for their antimicrobial activities against Escherichia coli and Staphylococcus aureus, both individually and in combination with ampicillin. Besides luteolin 7‐O‐glucoside, OLE and its major phenolic secondary metabolites were effective against both bacteria, with more activity on S. aureus. In combination with ampicillin, OLE, caffeic acid, verbascoside and oleuropein showed additive effects. Synergistic interaction was observed between ampicillin and hydroxytyrosol. The phenolic composition of OLE and the stability of olive phenols in assay medium were also investigated. While OLE and its phenolic secondary metabolites may not be potent enough as stand‐alone antimicrobials, their abilities to boost the activity of co‐administered antibiotics constitute an imperative future research area. Copyright

Olive (Olea europaea L.) Biophenols: A Nutriceutical against Oxidative Stress in SH-SY5Y Cells

Plant biophenols have been shown to be effective in the modulation of Alzheimer’s disease (AD) pathology resulting from free radical-induced oxidative stress and imbalance of the redox chemistry of transition metal ions (e.g., iron and copper). On the basis of earlier reported pharmacological activities, olive biophenols would also be expected to have anti-Alzheimer’s activity. In the present study, the antioxidant activity of individual olive biophenols (viz. caffeic acid, hydroxytyrosol, oleuropein, verbascoside, quercetin, rutin and luteolin) were evaluated using superoxide radical scavenging activity (SOR), hydrogen peroxide (H2O2) scavenging activity, and ferric reducing ability of plasma (FRAP) assays. The identification and antioxidant activities in four commercial olive extracts—Olive leaf extractTM (OLE), Olive fruit extractTM (OFE), Hydroxytyrosol ExtremeTM (HTE), and Olivenol plusTM (OLP)—were evaluated using an on-line HPLC-ABTS•+ assay, and HPLC-DAD-MS analysis. Oleuropein and hydroxytyrosol were the predominant biophenols in all the extracts. Among the single compounds examined, quercetin (EC50: 93.97 μM) and verbascoside (EC50: 0.66 mM) were the most potent SOR and H2O2 scavengers respectively. However, OLE and HTE were the highest SOR (EC50: 1.89 μg/mL) and H2O2 (EC50: 115.8 μg/mL) scavengers among the biophenol extracts. The neuroprotection of the biophenols was evaluated against H2O2-induced oxidative stress and copper (Cu)-induced toxicity in neuroblastoma (SH-SY5Y) cells. The highest neuroprotection values (98% and 92%) against H2O2-induced and Cu-induced toxicities were shown by the commercial extract HTETM. These were followed by the individual biophenols, caffeic acid (77% and 64%) and verbascoside (71% and 72%). Our results suggest that olive biophenols potentially serve as agents for the prevention of neurodegenerative diseases such as AD, and other neurodegenerative ailments that are caused by oxidative stress.

Phytochemistry, Ethnomedicine, and Pharmacology of Acacia

Abstract Acacia sensu lato is a large and widespread genus of the family Fabaceae with more than 1350 species. Taxonomically, this genus is complex and has undergone substantial controversial revisions recently. Acacia have been used as folk medicines for the treatment of a wide range of disorders including gastrointestinal, respiratory, eye, skin, teeth, blood, uterine, and endocrine problems. Gums (heteropolysaccharides) and condensed tannins (flavan-3-ol derivatives) are the most commonly reported constituents in Acacia. Pharmacological studies, at least in vitro, have demonstrated antioxidant, analgesic, antihypertensive, antidiabetic, anti-Alzheimer’s, and antimalarial effects of Acacia extracts. A number of secondary metabolites including phenols, alkaloids, and terpenoids, some with useful biological activities, have been reported in acacias. Very few species have been investigated for their phytochemical composition and biological activities. Hitherto, Acacia is largely an untapped resource of valuable secondary plant metabolites that have not gained enough scientific attention. This review aims to survey and critically appraise current literature on Acacia to provide sufficient baseline information for future work and potential commercial exploitation of Acacia.