Previously, the same authors reported on the extraction of phenolic compounds (PC) from flaxseed meal using a variety of extraction techniques (Akl et al. 2017). The wide range of biological activities of the components of the flaxseed meal (e.g., the introduction part), initiated our interest to evaluate the biological activities of these phenolic extracts (antioxidant, antimicrobial, anticoagulation, and anticancer effects).
Antioxidant activity of PC extracts from FM
All living organisms utilize oxygen to metabolize and use the dietary nutrients to produce energy for survival. Oxygen thus is a vital component for living. Oxygen meditates chemical reactions that metabolize fats, proteins, and carbohydrates to produce energy. While oxygen is one of the most essential components for living, it is also a double-edged sword. Oxygen is a highly reactive atom that can become part of potentially damaging molecules commonly called “free radicals,” which can attack the healthy cells of the body. This may lead to damage, disease, and severe disorders. Cell damage caused by free radicals appears to be a major contributor to aging and diseases like cancer, heart diseases, decline in brain function, and decline in immune system. Overall, free radicals have been implicated in the pathogenesis of at least 50 diseases.
Phenolic compounds are phytochemicals which play a major role in the protection of oxidation processes. The antioxidant properties of phenolic compounds can act as free radical scavengers, hydrogen donators, metal chelators, and singlet oxygen quenchers. It must be emphasized that most of the information on phenolic antioxidant potential comes from studies in vitro. There are several nutrients in food that contain antioxidants. Vitamin C, vitamin E, and β-carotene are among the most commonly studied dietary antioxidants [Chen et al. 1994; Malcolmson et al. 2000; Hosseinian et al. 2006].
Starting from the antioxidant activity and the following biological evaluations were all done on the semi-pilot scale prepared phenolic extract from FM.
The reducing power of a compound is related to its electron transfer ability and may serve as a significant indicator of its potent antioxidant activity. Fe+3/Fe+2 reducing power method is usually used for the determination of reducing power. In the reaction mixture, the presence of an antioxidant will reduce Fe+3 ferricyanide to Fe+2 ferrocyanide. The amount of Fe+2 can be determined by measuring the generation of Perl’s Prussian blue at 700 nm. Fu et al. (2014) concluded that all of three extracts of Jatropha curcas seed shell contained high contents of phenolic compounds and exhibited relatively strong antioxidant activities.
Slavova-Kazakova et al. (2016) studied antioxidant activity of flaxseed extracts in lipid systems. They reported that flaxseed extract, its alkaline hydrolysate, and SDG are not able to inhibit effectively lipid autoxidation in TGSO model. Both extracts act as natural antioxidants in a β-carotene-linoleate emulsion system. SECO exhibited a stronger activity than SDG.
Due to antioxidant properties in emulsion system, flaxseed extract and its hydrolysate can be used as natural antioxidants for meat, mayonnaise, and dressing, thus prolonging shelf life.
Toxicology test is known as a safety assessment and is conducted to determine the degree to which a substance can damage living or non-living organisms. The concentration of the chemical in air that kills 50% of the test animals during the observation period is the LC50 value. Other durations of exposure (versus the traditional 4 h) may apply depending on specific laws.
Phenolic antioxidants function as free radical terminators. Phenolic compounds and some of their derivatives are very efficient in preventing autoxidation; however, only a few phenolic compounds are currently permissible by law as food antioxidants. The major concerns for acceptability of such antioxidants are their activity and potential toxicity.
The antimicrobial activity of PC extract from FM
Phenolic compounds are produced by plants mainly for protection against stress and predators. The functions of phenolic compounds in plant physiology and interactions with biotic and abiotic environments are difficult to overestimate. Phenolics play important roles in plant development, particularly in lignin and pigment biosynthesis. They also provide structural integrity and support to plants. Importantly, phenolic phytoalexins, secreted by wounded or otherwise perturbed plants, repel or kill many microorganisms, and some pathogens can counteract or nullify these defenses or even disrupt them to their own advantage.
Thus, FM phenolic extract can be considered to have as antimicrobial activity. Gamal et al. (2011) working with guava seeds found the methanolic phenolic extract to exhibit antimicrobial activity. Taha et al. (2011) found that working with sunflower meal isolates chlorogenic acid (a phenolic compound) and that it had an antimicrobial activity and inhibited the growth of some food pathogens. Fernández-Lópeza et al. (2005) investigated the antioxidant and antibacterial effect of rosemary, orange, and lemon extracts in cooked Swedish-style meatballs. Activity in a lard system was established for all the extracts.
Flavanols have antioxidant, vasodilatory, anticoagulant, and anti-inflammatory properties. Flavanols have antidepressant effects on laboratory animals. Intake of flavanols enhances human cognitive performance and cerebral blood flow. Intake of flavanols such as dark chocolate counteracts negative emotions. Flavanol-rich cocoa-derived products may complement traditional antidepressant regimes.
Antihemorrhagic action of plant phenolic compounds is primarily due to compaction, increasing the strength of vascular tissue barriers. But there is a certain importance and influence of phenols on coagulation of blood. Hesperidin, rutin, and ellagic acid reduced the duration of bleeding. It is well known that the citrine, rutin, and other drugs increase the amount of calcium in the blood involved in the coagulation process. Finally, the acceleration of coagulation can be achieved indirectly—adrenaline promotes the formation of blood clots and phenolic compounds to protect it from inactivation in the bloodstream.
Wee et al. (2010), in conclusion, stated that the phenolic compounds in KRG have potent anticoagulant activity, whereas the saponin fractions, which were previously shown to possess antiplatelet aggregation activity, do not. Taken together, these results suggest that both saponins and phenolic compounds contribute to the cardiovascular effects of KRG through their antiplatelet aggregation and anticoagulant activities, respectively. Additionally, in vivo studies of the anticoagulant activities of phenolic compounds will be useful to better understand the pharmacology of these compounds.
The results of coagulant activity of the phenolic extract mean that PC caused hardly any clotting perhaps because the phenolics known to delay clotting time are not present according to HPLC analysis reported by Akl et al. (2017). Only p-coumaric and not coumaric was present as 9.3 μg/g meals in FM. Hesperidin, rutin, and ellagic acid reduced the duration of bleeding, and coumarin anticoagulants are bound to serum proteins.
Anticarcinogenic activity of PC from FM
Saenglee et al. (2016) stated that phenolic compounds present in our diet play an important role in colon cancer chemoprevention. Previous results demonstrated that peanut testa extract inhibited both histone deacetylase (HDAC) activity and the growth of colon cancer cells.
Flaxseed is extensively consumed in three ways: whole seed, powder, and flaxseed oil. In the last decade, flaxseed has gained attention due to its reported health benefits. Studies have shown the benefits of flaxseed alpha-linolenic acid (ALA), lignans, and fiber. The presence of these bioactive compounds helps in the prevention of cardiovascular diseases, diabetes, memory loss, and constipation. The phenolic compounds of flaxseed help in reduction of the fasting plasma glucose levels. Flaxseed contains biologically active estrogenic compounds called phytoestrogens which help in decreasing cell proliferation and prevents cancer. Higher levels of flaxseed are associated with prevention of memory loss and constipation. Flaxseed also contains several non-nutritional compounds such as cyanogenic glycosides, cadmium, trypsin inhibitors, and phytic acid that negatively influence health and well-being (Mishra and Verma 2013). Flaxseeds contain phenolic compounds called lignans, and secoisolariciresinol-diglucoside (SDG) is a major lignan with putative health benefits such as antioxidant and anticancer effects. The role of SDG and its metabolites such as enterolignans is gaining attention due to their mitigating effects against cancers especially prostate and breast cancer. Several epidemiological, in vitro and animal studies add evidence to this anticancer benefit of SDG. However, more research activities, especially clinical and pharmacokinetic studies in humans, are required to corroborate this evidence. The focus on the roles of SDG and its metabolites in preventing breast tumors, including an evaluation of potential mechanisms of action, was reviewed by Alphonse and Aluko (2015).