Peptide, and composition thereof and use thereof

A peptide represented by formula (I), or a stereoisomer thereof, or a mixture of stereoisomers thereof, or a salt thereof,

• in formula (I),
• X1 is selected from -Gly-, -Lys- or a bond;
• X2 is selected from -Nle-, -Val-, -Leu- or -Ile-;
• X3 is selected from -Lys-, -Arg- or -His-;
• X4 is selected from -Gly- or a bond;
• X5 is selected from -Ser- or a bond;
• R1 is selected from H or R3—CO—, wherein R3 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl;
• R2 is selected from —NR4R5 or —OR4, wherein each of R4 and R5 is independently selected from H, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl;
• the alkyl refers to a saturated aliphatic linear or branched chain alkyl having 1-24 carbon atoms (optionally having 1-16 carbon atoms;
• optionally having 1-14 carbon atoms;
• optionally having 1-12 carbon atoms;
• or optionally having 1, 2, 3, 4, 5, or 6 carbon atoms);
• optionally selected from methyl, ethyl, isopropyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, 2-ethylhexyl, 2-methylbutyl, or 5-methylhexyl;
• the alkenyl refers to a linear or branched chain alkenyl having 2-24 carbon atoms (optionally having 2-16 carbon atoms;
• optionally having 2-14 carbon atoms;
• optionally having 2-12 carbon atoms;
• optionally having 2, 3, 4, 5, or 6 carbon atoms);
• the alkenyl has one or more carbon-carbon double bonds, optionally has 1, 2 or 3 conjugated or non-conjugated carbon-carbon double bonds;
• the alkenyl is bonded to the rest portions of a molecule through a single bond;
• and is optionally selected from vinyl, oleyl, or linoleyl;
• optionally, the substituent in the “substituted alkyl” or “substituted alkenyl” is selected from C1-C4 alkyl;
• hydroxyl;
• C1-C4 alkoxy;
• amino;
• C1-C4 aminoalkyl;
• C1-C4 carbonyloxy;
• C1-C4 oxycarbonyl;
• halogen (such as fluorine, chlorine, bromine, and iodine);
• cyano;
• nitro;
• azide;
• C1-C4 alkylsulfonyl;
• thiol;
• C1-C4 alkylthio;
• C6-C30 aryloxy such as phenoxy;
• —NRb(C═NRb)NRbRc, wherein Rb and Rc are independently selected from H, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, C3-C10 cycloalkyl, C6-C18 aryl, C7-C17 aralkyl, a heterocyclic group having 3 to 10 members, or an amino protecting group.