The study, published in the Journal of Food Science, measured the total polyphenol contents and antioxidant activities of extractable polyphenols (EPPs) and non-extractable polyphenols (NEPPs) isolated from freeze-dried apple waste, and investigated their potential anti-cancer effects.
"Considerable amounts of polyphenolic compounds, which contain phytochemicals high in antioxidants... can be isolated from freeze-dried apple waste," said the researchers, led by Dr Said Ajlouni from the University of Melbourne, Australia.
They added that the industrial apple waste had a high volume of non-extractable polyphenols which had a significant inhibitory effect on human cancer cells.
"The antiproliferation study on human HeLa, HepG2, and HT-29 cancer cells showed that NEPPs at the concentration of 1 mg/mL had significant inhibitory effects against all tested cancer cells (46.2% to 95%), where EPP showed lower effect (3.9% to 22.2%)," said the research team.
"These results clearly indicated that NEPPs from industrial apple waste could be a good source of natural antioxidants with significant antiproliferation efficacy against human cancer cells," they added.
Study details
The researchers prepared freeze-dried apple waste samples from locally sourced apple processing plants, which were then ground into powder using porcelain pestle and mortar and evaluated for antioxidant content.
Ajlouni and his team reported that industrial apple waste had a total polyphenolic content in nonextractable polyphenols (NEPPs) of 539.84 mg in comparison to 77.26 mg of extractable polyphenols (EPPs).
They said that both antioxidant isolates (EPPs and NEPPs) showed very strong antioxidant activities, but noted that the results “demonstrated that NEPPs had significantly higher rate of radical scavenging capacity than EPPs.”
“These findings strongly suggested that studies of freeze-dried apple and other fruits and vegetables waste extracts should be further carried out in vitro using appropriate laboratory animal models of cancer and ultimately in human cancer prevention trials,” they said.
Waste no more
The researchers noted that excess amount of oxidants in human body can lead to oxidative stress, resulting in DNA and protein damages and an increase in the risks of degenerative diseases such as cancer.
“It has been reported that cardiovascular diseases and cancers are the leading causes of death in the world. However, studies suggested that dietary modification can reduce deaths from cancer by 20% to 42% and plays an essential role in the prevention of chronic diseases,” they said.
They added that agricultural by-products in general “contain a variety of biologically active compounds that are mostly going to waste.”
“For instance, apple peels represent up to 10% of the whole apple fruit ... However, these antioxidant-rich fruit tissues are often discarded during processing, packaging, and canning,”
Ajlouni and his colleagues said that estimates suggest that that fruits processing generates solid waste as high as 50% of raw material, consisting of peel, core, pomace, unripe fruits, cull fruits, and mechanically damaged fruits.
“Clearly, apple peels could be an excellent source of natural antioxidants and bioactive compounds that may contribute to human health improvement,” they argued.
Source: Journal of Food Science
Volume 76, Issue 7, pages T163–T172, doi: 10.1111/j.1750-3841.2011.02314.
“Antioxidant and Antiproliferation Effects of Extractable and Nonextractable Polyphenols Isolated from Apple Waste Using Different Extraction Methods”
Authors: W.W. Tow, R. Premier, H. Jing, S. Ajlouni