The yield of Ananas comosus (pineapple) is susceptible to microbial infection and the usage of chemical pesticides to control it has been often associated with negative impacts to the environment and human health. As pineapple leaves is one of the lavish organic materials with antimicrobial properties due to its total phenolic content (TPC), its potential as a microbial inhibitor is explored in this study. The objective of this research is to study the factors that affect microbe growth inhibition using pineapple leaves juice (PLJ). The factors evaluated were; reaction time between mixtures of PLJ and microbe (0.5 – 5 hours), concentration of TPC in PLJ (0.2563 – 0.5127 mg GAE/ml), reaction temperature (26 – 37°C), and ratio of microbe to PLJ (M/PLJ) (1:1 and 1:3). A two level factorial design was adopted to assess the effect of the above mentioned factors on the microbial inhibition by PLJ. The results show that the most contributing factor of 1.55 % was reaction temperature, meanwhile the highest contribution factor for interaction effect was between concentration of TPC in PLJ and ratio of microbe to PLJ at 5.17%. The best condition for microbe growth inhibition of 20.90% was found to be at reaction time of 0.5 hour, TPC in PLJ of 0.5127 mg GAE/ml, reaction temperature of 37°C, and M/PLJ at 1:1. This study demonstrates that pineapple leaves could be exploited as valuable sources of natural products that could be used as microbial growth inhibitor and thus become one of the cheap and green alternatives for more expensive chemical pesticides.

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Since pineapple leaves are one of the lavishly organic waste materials which contain phenolic compounds with antimicrobial properties, it was desired to gain deeper knowledge on its potential as microbial growth inhibitor (MGI). In this research, the pineapple leaves were extracted using an electrical sugarcane pressing machine to acquire the pineapple leaves juice (PLJ). The PLJ was autoclaved at 121 °C for 15 min. Ultra-high-performance liquid chromatography-quadrupole time of flight mass spectroscopy (UPLC-QTOF-MS) analysis was used to examined the existence of different bioactive components in PLJ. Based on the molecular mass and its fragmentation pattern, the identification of the phenolic compounds was confirmed. From the characterization of PLJ using UPLC-QTOF-MS, seven types of the phenolic compound has been identified namely Octahydrocurcumin, Meliadanoside A, Kukoamine A, Stilbostemin D, Agrimol C, Feralolide and Methyl-5-O-caffeoylquinate. The effect of microbial inhibition time on the colony forming unit (CFU) between the mixtures of PLJ and microbe was studied. CFU/mL decreased with increasing microbial inhibition time from 0 to 1.50 h. Meanwhile, CFU/mL was increased again after increasing the microbial inhibition period from 1.50 to 3 h. This suggests that 1.50 h was necessary for the process of microbial growth inhibition. This research shows that pineapple leaves could be manipulated and used as an MGI agent as useful sources of natural products. Furthermore, it can become one of the cheaper and greener MGI alternatives compared to available synthetic antimicrobial agent.

This study optimized microbial growth inhibition conditions using pineapple leaf juice (PLJ). The sugarcane press machine was used to press the PLJ. The study considered four factors to be analyzed by Two-level factorial design (TLFD), which are microbial inhibition time (0.5–5 h), the concentration of total phenolic content (TPC) (0.2563–0.5127 mg GAE/ mL), temperature (26–37 °C), and the ratio of PLJ to microbe (PLJ/M) (v/v) (1:1 and 1:3). Colony-forming unit (CFU) method was employed to measure microbial growth inhibition. The microbial growth inhibition was expressed as a percent in terms of CFU/mL. A central composite design (CCD) experimental design created using response surface methodology (RSM) determined the optimum temperature (35–39 °C) and microbial inhibition time (10–50 min) of microbial growth inhibition. The best conditions were 0.5 h of microbial inhibition time, 0.5127 mg GAE/mL of TPC, 1:1 PLJ/M, and a temperature of 37 °C. The analysis of variance (ANOVA) showed that temperature (Factor C) has the greatest contribution (1.56%) to inhibiting microbial growth, accompanied by TPC concentration in PLJ (Factor B) with 1.27%, microbial inhibition time (Factor A) with 1.07% and PLJ/M (Factor D) 0.29%. Optimization studies show that at an optimum temperature of 37 °C and an inhibition time of 34.25 min, maximum microbial growth inhibition of 94.73% with a minimum value of 9.12×104 CFU/mL was achieved. This research suggests that PLJ can be utilized as a value-added natural product for application in the agricultural sector.