A Colored Avocado Seed Extract With Antioxidant, Anti-carcinogenic And Anti-inflammatory Effects

Open Access
Author:
Dabas, Deepti
Graduate Program:
Food Science
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
November 29, 2011
Committee Members:
  • Joshua D Lambert, Dissertation Advisor
  • Gregory Ray Ziegler, Dissertation Advisor
  • Ryan John Elias, Committee Member
  • Steven M Weinreb, Committee Member
Keywords:
  • avocado seed
  • natural colorant
  • antioxidant
  • anti-cancer
  • anti-inflammatory
  • polyphenol oxidase
Abstract:
There is an increasing consumer demand for and scientific interest in new functional food ingredients. Avocado is a commercially important crop and studies have shown that the pulp may have benefits to cardiovascular health, dermatological health and possibly anti-cancer activity. Despite being important historically, the avocado seed is considered a waste product and does not find uses currently. New research is beginning to show its potentially useful functional properties. We report here that avocado (Persea americana) seed when crushed with water develops an orange color in a time-dependent manner. Heat treatment of the seed prevented color development, whereas addition of exogenous polyphenol oxidase (PPO) restored color development. The orange color intensified as the pH was adjusted from 2.0 to 11.0 in solution, and these changes were only partially reversible in the presence of oxygen but completely reversible when the pH was adjusted and readjusted in the absence of oxygen. The color was found to be stable in solution form at -18 oC for two months at pH 7.5. The colored avocado seed extract (CASE) was found to have radical scavenging activity, by electron paramagnetic resonance spectroscopy (EC50 = 42.1 g/mL) and antioxidant activity in oil-in-water emulsions. The oxygen radical absorbance capacity (ORAC) value of CASE was 2012.1 ± 300 TE/mg. CASE inhibited the growth of human cancer cell lines (lung, colon, breast, and prostate) (IC50= 19.1-132.2 μg/mL) in vitro. LNCaP prostate cancer cells were the most sensitive to the effects and further studies showed that CASE inhibited cell cycle progression in the G0/G1 phase by decreasing expression of cyclin D1 and cyclin E2. Further it induced apoptosis as indicated by cleavage of caspase 3, cleavage of poly (ADP –ribose) polymerase (PARP) and externalization of phosphatidylserine. It also reduced the nuclear translocation of NF-κB, a transcription factor which promotes cell survival and replication. In lipopolysaccharide (LPS)-stimulated RAW 264.7 murine macrophages, CASE reduced the formation of pro-inflammatory cytokines (IL-6, IL-1β and TNFα), and NO, a potent inflammatory mediator. Reduced NO production correlated with reduced iNOS expression. CASE reduced the formation of Prostaglandin E2, a pro-inflammatory mediator and inhibited Phospholipase A2 (IC50 = 36 µg/mL) by a non-competitive mechanism. CASE reduced LPS-induced nuclear translocation of NF-κB, transcription factor with pro-inflammatory actions. Overall, these results suggest that the avocado seed may be a potential source of natural colorant which could impart additional functions including radical scavenging, cancer preventive activity and anti-inflammatory activities. However these effects need to be further tested in vivo.