다양한 빛 조사 및 용매 조건에서 curcumin의 광반응성, 광안정성 및 산화방지 활성의 변화 = Changes in photoreactivity, photostability, and antioxidant property of curcumin in different solvent systems under irradiation of different light sources

다국어 초록 (Multilingual Abstract)

Curcumin exhibits various bioactive functions but is chemically unstable and poorly soluble in water. This study investigated the effects of different emulsion stabilizers including polyvinyl alcohol (PVA), polyethylene glycol, polysorbate 80 (PS), sucrose stearate, and lecithin on the color intensity, photostability, and antioxidant properties of curcumin. PVA and PS significantly enhanced the color intensity of curcumin. Additionally, color degradation was accelerated under light exposure in the following order: blue light emitting diode (LED), fluorescent light, white LED, green LED, and red LED irradiation. PVA significantly delayed the color degradation of curcumin under all the tested light sources. PS also improved the photostability of curcumin under green LED irradiation but not under other light sources. The antioxidant activity of curcumin, assessed through 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) radical scavenging assays, was enhanced in the presence of PVA, whereas its ferric reducing antioxidant power (FRAP) was not improved.
To address these limitations in aqueous-based formulations, this study evaluated the photochemical properties and antioxidant activity of curcumin under diverse solvent environments and polyvinyl alcohol (PVA)-stabilized conditions, including assessments of photosensitivity and photostability in aqueous media containing 1–5% PVA with varying hydrolysis degrees (99%, 87–89%, and 80%). The absorbance spectra of curcumin in various solvents revealed that aprotic solvents induced a sharp absorbance peak corresponding to the enol form, while protic solvents shifted the equilibrium toward the keto form, resulting in broader peaks. Under alkaline conditions, curcumin was converted into enolate ions, leading to a red-shift in the absorbance maxima. When exposed to 10 W/m² blue LED light, both photoreactions and curcumin degradation were accelerated in acetone and acetonitrile, whereas these processes proceeded more slowly in methanol and ethanol. PVA with 87-89 or 80% hydrolysis degrees significantly improved solubility and optical clarity of curcumin in an aqueous solution, allowing for reliable quantification of photodegradation and photosensitivity in the assay using MTT formazan probe. Less than 1% concentrations, 99% hydrolyzed PVA enhanced photostability of curcumin, but induced aggregation of curcumin and formazan at higher concentrations. Antioxidant capacity of curcumin in an aqueous solution, evaluated based on ABTS and AAPH radical scavenging assays, was also enhanced in the presence of PVAs; ABTS activity increased with 99% hydrolyzed PVA, while AAPH radical scavenging activity was greater with 80% hydrolyzed PVA. However, its FRAP reducing power was not improved. These results indicate that different emulsion stabilizers modulate the solubility, photostability, and bioactivity of curcumin in aqueous solutions, and PVA could provide a practical approach to improve the physicochemical stability and functional efficacy of curcumin in aqueous formulations.

목차 (Table of Contents)

• Part Ⅰ. 다양한 광원과 유화안정제에 의한 curcumin의 화학적 특성 및 생리활성 변화
• 1. 서론 2
• 2. 재료 및 방법 4
• 2.1. 시약 및 LED 조사 장치 4
• 2.2. 빛 조사에 따른 curcumin의 흡광 특성 및 광안정성 평가 4
• 2.3. 산화방지활성 평가 5
• 2.4. 통계처리 6
• 3. 결과 및 고찰 10
• 3.1. 안정제 및 유화제에 의한 curcumin의 흡광 특성 변화 10
• 3.2. 형광등 조사에 따른 curcumin의 광안정성 평가 14
• 3.3. 다양한 LED 조사 하에서 안정제 및 유화제의 영향 20
• 3.4. 안정제 및 유화제에 의한 curcumin의 산화방지활성 변화 28
• 4. 결론 34
• Part Ⅱ. 용매와 polyvinyl alcohol (PVA) 안정화 조건에 따른 curcumin의 광화학적 특성 및 산화방지활성 변화
• 1. 서론 36
• 2. 재료 및 방법 39
• 2.1. 시약 및 LED 조사 장치 39
• 2.2. 용매와 PVA 안정화 조건에 따른 curcumin의 흡광 특성, 안정성 및 감광성 평가 39
• 2.3. PVA 안정화 조건에 따른 curcumin의 산화방지활성 평가 40
• 2.4. 통계처리 41
• 3. 결과 및 고찰 42
• 3.1. 다양한 용매에서의 curcumin 광반응성 변화 42
• 3.2. PVA에 의한 curcumin의 광안정성 변화 50
• 3.3. PVA에 의한 curcumin의 산화방지활성 변화 54
• 3.4. 고농도 PVA에 의한 curcumin의 수용화 및 흡광도 변화 59
• 3.5. 고농도 PVA에 의한 curcumin의 광안정성 및 감광성 조절 효과 62
• 4. 결론 69
• 참고문헌 70
• ABSTRACT 74