Establishment of a determination method of MAPs in banana fruit and study on its content variation rule

【Objective】To establish an method for accurate and rapid determination of monoamines and their precursors（MAPs）in banana fruit，to clarify the changes in the content of MAPs components during banana fruit development，so as to provide reference for analyzing its anabolic mechanism in the next step.【Method】Bnana fruits of three banana varieties，Baxi，Dongguan Dajiao and Fenza 1 were taken as tested material. The reversed-phase high performance liquid chromatography-ultraviolet（RP-HPLC-UV）was used to determine the contents of MAPs in pulp and peel of Baxi，Fenza 1 and Dongguan Dajiao were detected from 15 to 75 days after cutting bud，to study how MAPs changed during the fruit development.【Result】A C₁₈ column（4.6×250 mm，5 µm）was connected to the RP-HPLC-UV platform. Methanol and 0.1% trifluoroacetic acid aqueous solution were used as mobile phase A and B respectively. Then the contents of norepinephrine（NE），dopamine（DA），levodopa（L-dopa），tyramine（TYRA），tyrosine（Tyr），serotonin（SERO），tryptamine （TRM）and tryptophan（Trp）were determined. The spiked recoveries range was 95.3% to 106.1%，the intra-day precision ranges was 0.37% to 0.82%，and the inter-day precision ranges was 0.35% to 0.83%；the detection limit was 0.0012 to 0.0016 mg/100 g，the limit of quantification was 0.0040 to 0.0053 mg/100 g；a sample can be completely detected within 14 minutes. During fruit development of the three banana varieties，the contents of TRM，TYRA，L-dopa，NE and DA in the peel were higher than those in the pulp. In addition，the contents of SERO，Trp and Tyr in the peels of Dongguan Dajiao and Fenza 1 were higher than those in the pulp，while the contents of Trp and Tyr in the peels of Baxi were lower than those in the pulp. The contents of most MAPs increased rapidly in the early stage of fruit development in Baxi pulp，reaching the peak around 30 days after cutting bud，the contents of NE，DA，TYRA，Tyr，Trp and TRM were 22.14，239.81， 118.29，43.74，46.41 and 5.33 mg/100 g. After that，the contents of NE，DA，TYRA and TRM reached the lowest point when the fruit matured，and the contents were 3.17，7.08，12.58 and 1.04 mg/100 g，respectively. However，the lowest point contents of Tyr and Trp appeared around 45 days after cutting bud. The contents of TYRA and SERO in Dongguan Dajiao and Fenza 1 showed a downward trend during fruit development.【Conclusion】An accurate，sensitive and rapid RP-HPLC-UV method is established，which can be used for quantitative detection of MAPs in banana fruits. 8 MAPs，such as NE，DA，Ldopa，TYRA，Tyr，SERO，TRM，Trp were detected in the flesh and peel of three banana varieties at different developmental stages，and their contents in the fruit of Baxi show a significant difference from that of Dongguan Dajiao and Fenza 1.