Wasted potential? Traditionally discarded, avocado seed and leaf extracts may promote health

18 Mar 2019 --- Although inedible in their original form, avocado leaves and seeds contain oils and compounds that can benefit health. This is according to two new studies, which found that avocado seed oil and avocado leaf possess anti-inflammatory properties and antioxidant compounds, respectively, that may prevent a number of diseases such as hypertension and cardiovascular disease. The studies flag the potential nutritional benefits of parts of the avocado that are traditionally discarded and note that these may, in fact, hold value for the food industry.

Anti-inflammatory avocado seed extract 
According to a Pennsylvania State University (Penn State) study, published in Advances In Food Technology and Nutritional Sciences, an extract derived from avocado seeds showed anti-inflammatory properties and may be used as a functional food ingredient or in pharmaceuticals. As a food colorant, avocado seed extract offers a vibrant orange color. The researchers, having worked on the extract for the past ten years, have filed a patent for its use as a food color additive. Joshua Lambert, Associate Professor of Food Science at Penn State, notes that it is not known whether the intense color plays any part in inhibiting pro-inflammatory mediators. 

Using cell culture models and enzymes that are important in immune response and inflammatory diseases, the researchers tried to determine the anti-inflammatory properties of avocado seed extract. Macrophages, a class of immune cells, were cultured in petri dishes and activated with a pro-inflammatory stimulus in the presence of the avocado seed extract. Following treatment with the avocado seed extract, the authors also measured the production of significant pro-inflammatory mediators and signaling pathways in the cells.

“The next step, before we can draw further conclusions about the anti-inflammatory activity of this avocado seed extract, will be to design animal model studies,” says Lambert. 

Researchers Gregory Ziegler (left) and Joshua Lambert (right) along with Rachel Shegog, a food science graduate student, examine a sample of bright orange liquid extracted from avocado seeds that has been shown to have anti-inflammatory properties.Lambert supports that further research is warranted and this study is “laying the groundwork” for it. “The level of activity that we see from the extract is very good,” he says. “We saw inhibitory activity at concentrations in the low microgram-per-milliliter range, which is an acceptable amount of activity to justify further studies.”

The researchers also mention that the findings are important because chronic inflammation is linked to cancer, cardiovascular diseases and other serious conditions, especially since avocado pits are presently discarded.

“If we can return value to avocado growers or avocado processors, that would be a benefit,” he notes. “And if we can reduce the amount of this material being dumped in landfills, that would be a good thing, given the huge amount of avocados that are consumed. This is encouraging because there is a market for other high-value sources of bioactive compounds we have tested, such as cocoa and green tea – whereas avocado seeds are essentially considered to be waste.”

Potential health benefits from avocado leaves
Avocado seeds may not be the only part of the Instagram-favorite fruit that may benefit health. Research from the University of Nuevo León in Mexico found that the leaves of the locally-grown Persea americana variety are rich in phytochemical compounds that offer significant antioxidant activity and may treat certain diseases. The researchers found 41 compounds, predominantly phenolic acids and flavonoids, 18 of which were identified for the first time in such plant material.   

Traditionally, avocado leaves were used in Latin American medicine to treat coughs, bruising, wound healing and hypertension. 

“The present study demonstrates that avocado leaves represent an important source for the recovery of added-value compounds with high antioxidant activity. These compounds have potential applications as bioactive antioxidant agents for the treatment of several diseases and in the development of novel food products,” note the researchers.

The study published in Molecules comes at a time when avocado consumption is seeing increased popularity. This has caused a high volume of agri-industrial by-product waste before and after pruning and production, with seeds, peels and leaves discarded with no further applications, according to the researchers. 

These by-products may prove a “rich source of bioactive compounds,” as well as functional ingredients such as minerals, vitamins, fatty acids, proteins, fibers and polyphenols such as phenolic acid. 

Reportedly, the polyphenol compounds are associated with fighting degenerative disease and having anti-inflammatory, hypocholesterolemic and anticancer properties.

The researchers assessed the scavenging capacity of free radicals and inhibitory effects on lipid oxidation. The results showed a “statistically significant effect on the antioxidant activities.”

“In agreement with our results, previous studies have shown that the effectiveness of avocado extracts against lipid oxidation is linked to the phenolic contents in peels, seeds and leaves,” the researchers note. For example, a previous study showed that the extracts could prevent lipid oxidation in chilled pork patties and another confirmed them as antimicrobial agents. 

Additionally, via analysis, the study characterized the phytochemical compounds found in leaf extracts and identified 35 phenolic compounds. Additional testing showed that phytochemical profiles differed among cultivars. The most “diverse” cultivar contained 25 compounds and the least diverse contained a mere 16 compounds. 

“Phytochemical diversity and variation are evident when cultivars are compared, which could be the result of the genetic constitution as they were grown under same climatic conditions and samples were taken from mature and productive avocado trees,” the researchers say. 

The researchers do note, however, that further research on the matter is warranted to determine this particular genotype correlation.