The pulp of avocado (Persea americana, Lauraceae) has been reported to have beneficial cardiovascular health effects. Avocado oil is used for dermatological applications and its unsaponifiable portion is reported to have beneficial effects against osteoarthritis. Although the seed represents a considerable percentage of the total fruit, scientific research on the phytochemistry and biological effects of avocado seeds is in the nascent stages,. Currently, the seed represents an under-utilized resource and a waste issue for avocado processors. There is ethno-pharmacological information on the use of seeds for the treatment of health-related conditions, especially in South American countries where avocados are endemic and currently grown on a large scale. Current research has shown that avocado seeds may improve hypercholesterolemia, and be useful in the treatment of hypertension, inflammatory conditions and diabetes. Seeds have also been found to possess insecticidal, fungicidal, and anti-microbial activities. The avocado seeds and rich in phenolic compounds, and these may play a role in the putative health effects. Historically, extracts of avocado seeds were also used as ink for writing and research in our laboratory has explored the potential colorant properties of a polyphenol oxidase-produced colored avocado seed extract. Here, we review the currently-available data on the bioactivity and other functional properties of avocado seeds. We discuss the strength of the available data, the putative active compounds, and potential directions for future studies.
Avocado (Persea americana) seeds have been used traditionally for a number of health-related indications. Because of its high polyphenol content, we investigated the potential antioxidant and anticancer effects of a colored avocado seed extract (CASE). CASE exhibited an oxygen radical acceptance capacity value of 2012 ± 300 trolox equivalents/mg. CASE reduced lipid hydroperoxide formation in an oil-in-water emulsion (33% reduction at 500 μg/mL). CASE dose-dependently reduced the viability of human breast (MCF7), lung (H1299), colon (HT29), and prostate (LNCaP) cancer cells in vitro. The half maximal inhibitory concentrations ranged from 19 to 132 μg/mL after treatment for 48 h. CASE treatment downregulated the expression of cyclin D1 and E2 in LNCaP cells. This was associated with cell G0/G1 phase cycle arrest. CASE also dose-dependently induced apoptosis in LNCaP cells. CASE reduced nuclear translocation of nuclear factor κB, a prosurvival signal. Further studies are needed to examine these effects in in vivo models.
There is growing public and scientific interest in the development of natural alternatives to synthetic colorants in foods. Extracts of turmeric, paprika, and beets are examples of food-derived natural colorants. Avocado seeds, which represent an under-utilized waste stream, form a stable orange color when crushed in the presence of air. Our data indicate that avocado seed represents a potential source of new natural colorants for use in foods.
The market for natural colors for food applications is ever increasing. Consumers are seeking simpler and cleaner labels for their foods and are looking for alternatives to synthetic ingredients. As a result, interest in natural products including natural colorants is obvious. This review explores the potential of polyphenols and polyphenol derived molecules as colorants. Polyphenols are classified into flavonoids or non-flavonoids and are known for their antioxidant and biological activity. Anthocyanins are well known colored flavonoids but other polyphenols including many aurones and chalcones derivatives are also colored. Curcumin, demethoxyxurcumin, bisdemethoxycurcumin and cyclocurcumin are isolated from turmeric. Turmeric extract is used as a colorant in many food applications owing to its high heat stability. Anthraquinone based pigments occur in nature, one of which is tetrahydroxylated anthraquinone-carminic acid. Carminic acid and its lake are commonly used pigments and provide a red to pink hue depending on pH of a food or beverage. Usually colorless polyphenols can give rise to colored products by virtue of presence of enzymes or reaction with other substrates or both. Polyphenol oxidase (PPO) plays an important role in these reactions. Typically polyphenol content is lower after these reactions occur. Tea pigments are a good example where PPO oxidizes Epicatechin and epicatechin-3-O-gallate (EGCG) and other polyphenols. The reaction products being very unstable in nature interact chemically and generate pigments. During cocoa processing the nibs undergo fermentation, leading up to enzymatic reactions causing color development at the expense of polyphenols. Avocado seeds undergo similar reactions in presence of PPO and oxygen. Similarly in wine, new pigments called pyranoanthocyanins are generated from anthocyanins. During juice extraction in apples, colored products are formed from colorless chalcones as a result of PPO activity. PPO products have been thought to be polymeric in nature but in the reviewed studies that is not the case. Among the polyphenols discussed in the study, aurones, chalcones and Hydroxy-anthraquinones (HAQs) have not been exploited to full potential. More research on optimizing isolation of pigments and using in food systems is needed. Regulatory hurdles will need to be cleared to enable their use in food applications.
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