Method of improving stability of sweet enhancer and composition containing stabilized sweet enhancer

A liquid composition comprising a sweet enhancer having structural formula (Ib) or (I′b),

• and
• a phenol-based antioxidant, or a salt or solvate thereof, as a photostabilizer,
• wherein:
• A is —OR1, —NR1, —NR1C(O)R2, —NHOR1, —NR1R2, —NR1CO2R2, —NR1C(O)NR2R3, —NR1C(S)NR2R3 or —NR1C(═NH)NR2R3;
• B is hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, acyl, substituted acyl, heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl, or substituted heteroarylalkyl;
• C is —OR7, —S(O)bR7, —SO3R7, —C(O)NR7R8, —CO2R7, —NR7CO2R8, —NR7C(O)NR8R9, —NR7C(═NH)NR8R9, —SO2NR7R8, —NR7SO2R8, —NR7SO2NR8R9, —B(OR7)(OR8), —P(O)(OR7)(OR8), —P(O)(R7)(OR8), or heteroaryl;
• b is 0, 1 or 2;
• R1, R2, R3, R7, R8, and R9 are independently hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, acyl, substituted acyl, heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl or substituted heteroarylalkyl;
• or alternatively, R1 and R2, R2 and R3, R7 and R8, or R8 and R9, together with the atoms to which they are bonded, form a cycloheteroalkyl or substituted cycloheteroalkyl ring;
• L1 is alkylene or substituted alkylene;
• L2 is —NR34—, —O—, —S—, —NR34—C(O)—, —C(O)—NR34—, —O—C(O)—, —C(O)—O—, —NR34—C(O)—O—, —O—C(O)—NR34—, —NR34—C(O)—NR35—, —O—C(O)—O—, -heterocyclylene-C(O)—, or -(substituted heterocyclylene)-C(O)—;
• R33 is alkyl, substituted alkyl, carbocyclyl, substituted carbocyclyl;
• aryl, substituted aryl, arylalkyl, substituted arylalkyl, heterocyclyl, substituted heterocyclyl, heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl, or substituted heteroarylalkyl;
• and
• R34 and R35 are independently hydrogen, alkyl, substituted alkyl, carbocyclyl, substituted carbocyclyl;
• aryl, substituted aryl, arylalkyl, substituted arylalkyl, heterocyclyl, substituted heterocyclyl, heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl, or substituted heteroarylalkyl.

A liquid composition comprising a sweet enhancer having structural formula (Ic), (I′c), (Id), or (I′d),

• and a phenol-based antioxidant, or a salt or solvate thereof, as a photostabilizer,
• wherein:
• A is —OR1, —NR1C(O)R2, —NHOR1, —NR1R2, —NR1CO2R2, —NR1C(O)NR2R3, —NR1C(S)NR2R3 or —NR1C(═NH)NR2R3;
• B is hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, acyl, substituted acyl, heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl, or substituted heteroarylalkyl;
• C is —OR7, —S(O)bR7, —SO3R7, —C(O)NR7R8, —CO2R7, —NR7CO2R8, —NR7C(O)NR8R9, —NR7C(═NH)NR8R9, — SO2NR7R8, —NR7SO2R8, —NR7SO2NR8R9, —B(OR7)(OR8), —P(O)(OR7)(OR8), —P(O)(R7)(OR8), or heteroaryl;
• b is 0, 1 or 2;
• R1, R2, R3, R7, R8, and R9 are independently hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, acyl, substituted acyl, heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl or substituted heteroarylalkyl;
• or alternatively, R1 and R2, R2 and R3, R7 and R8, or R8 and R9, together with the atoms to which they are bonded, form a cycloheteroalkyl or substituted cycloheteroalkyl ring;
• R33 is alkyl, substituted alkyl, carbocyclyl, substituted carbocyclyl;
• aryl, substituted aryl, arylalkyl, substituted arylalkyl, heterocyclyl, substituted heterocyclyl, heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl, or substituted heteroarylalkyl.

A liquid composition comprising a sweet enhancer having structural formula (Ie):

• and a phenol-based antioxidant, or a salt or solvate thereof, as a photostabilizer,
• wherein:
• R1 and R2 are independently hydrogen or C1 to C6 alkyl;
• L is C1 to C12 alkylene or substituted C1 to C12 alkylene;
• M is —NR4—C(O)— or —C(O)—NR4—;
• R4 is hydrogen or C1 to C6 alkyl;
• or alternatively, when M is —NR4—C(O)—, R4 and one or more atoms of L, together with the nitrogen to which they are attached, form a 5- to 8-membered heterocyclic ring which is optionally substituted and contains one to three heteroatoms selected from nitrogen, oxygen, and sulfur;
• and
• R3 is C1 to C12 alkyl, substituted C1 to C12 alkyl, 5- to 8-membered heterocyclyl, or substituted 5- to 8-membered heterocyclyl;
• or alternatively, when M is —C(O)—NR4—, R4 and one or more atoms of R3, together with the nitrogen to which they are attached, form a 5- to 8-membered heterocyclic ring which is optionally substituted and contains one to three heteroatoms selected from nitrogen, oxygen, and sulfur.