1 H-cyclopropa[b]naphthalene: a novel ethylene antagonist for extending storage life and maintaining quality of climacteric and suppressed climacteric plums

Abstract

AbstractEthylene is a key trigger that governs the rate of fruit ripening, storability, and postharvest quality of fresh fruit. Efficient inhibition of ethylene action is essential to slow down the postharvest ripening processes, extend storage life and maintain optimum fruit quality during storage. Ethylene antagonist compounds with the likelihood of application as liquid formulation would facilitate managing ethylene broadly as both preharvest and/or postharvest treatments. This study examined the effects of different aqueous formulations of 1 H-cyclopropa[b]naphthalene (NC) as an ethylene antagonist in the cold stored (1 °C) Japanese plums ‘Angeleno’ (suppressed-climacteric) and ‘Tegan Blue’, which exhibit climacteric peaks, respectively. NC was applied as a 2 µM spray solution prepared using only distilled water (NCA), 5% ethanol (NCE), 0.02% Tween® 20 (NCT), 5% β-cyclodextrin (NCD) or a 1 µM fumigant for 18 h at ambient conditions (20 ± 1 °C). Regardless of formulation, NC retarded ethylene production in both the suppressed-climacteric and climactic cultivars. The capacity of NC to suppress ethylene production was relatively higher in ‘Angeleno’ than in ‘Tegan Blue’. Levels of bioactive compounds such as total phenols, total anthocyanins and total antioxidant capacity in fruit treated with NC were at par with the control. NC fumigation was the most effective treatment in suppressing ethylene production and maintaining fruit quality followed by NCE, NCT, NCD and NCA in both plum cultivars. Amongst the NC spray solutions, the ones with ethanol or Tween® 20 as adjuvants outperformed other solutions. Ethylene production positively correlated with weight loss, SSC, SSC: TA and concentrations of individual sugars, but was negatively correlated with firmness, titratable acidity (TA) and individual organic acids in both cultivars. The results also support the notion that ethylene has a role in the synthesis of phenolic compounds and anthocyanin depending on the sugar substrates present in the phenylpropanoid and flavonoid pathways.