退黑激素

melatonin

abbr. for Heilongjiang province 黑龍江|黑龙江[Hei1 long2 jiang1]

black / dark / sinister / secret / shady / illegal / to hide (sth) away / to vilify / (loanword) to hack (computing)

to retreat / to decline / to move back / to withdraw

to retreat; to withdraw / to reject; to return (sth) / to decline

raw silk / white / plain, unadorned / vegetarian (food) / essence / nature / element / constituent / usually / always / ever

to arouse / to incite / to excite / to stimulate / sharp / fierce / violent

hormone