Curcumin, together with its analogs, namely, demethoxycurcumin and bisdemethoxycurcumin, are phenolic pigments extracted from turmeric. These curcuminoids are considered to be a potent antioxidants possessing a multitude of properties including anti-inflammatory, antitumor, anti-HIV and antimicrobial properties. One of the serious drawbacks of these curcuminoids as therapeutic agent is their fast degradation at physiological pH leading to poor bioavailability in the biological milieu. With a view to address this stability issue we synthesized curcuminoid-silver nanoparticle (CUR-AgNP) complexes, utilizing curcuminoids as reducing agents. The stability of individual curcuminoids in the CUR control and in the CUR-AgNP complex was compared after incubation in phosphate buffer of pH 7.4. Interestingly the initial degradation of curcuminoids at 4 h was only 9.6% in the CUR-AgNP complex when compared to 49.6% degradation observed in the CUR control. Among the three curcumin analogs, bisdemethoxycurcumin showed better pH stability compared to curcumin and demethoxycurcumin whereas all the three curcuminoids exhibited the same degradation pattern in the case of the CUR-AgNP complex. In vitro studies with the CUR-AgNP complex showed excellent antibacterial property against P. aeruginosa. CUR-AgNP complex also exhibited good cytotoxic effect on MDA-MB231 cells. The storage stability of CUR-AgNP complex, kept as a suspension at room temperature ($\sim$28 ${}^{\mathrm{o}}$C), was tested by measuring its hydrodynamic size and zeta potential. It was found that after 340 days of storage the particle size (Z-average) and zeta potential were 65.5 ± 1.1 nm and -22.9 ± 0.2 mV, respectively, indicating that the nanoparticle suspension was stable The results obtained in the present study are promising and could be extended to improve the therapeutic efficacy of curcuminoids in the biological pH conditions.

姜黄素及其类似物，即去甲氧基姜黄素和双去甲氧基姜黄素，是从姜黄提取的酚醛颜料。这些姜黄素被认为是有效的抗氧化剂，具有多种特性，包括抗炎，抗肿瘤，抗HIV和抗菌特性。这些姜黄素作为治疗剂的严重缺陷之一是它们在生理pH下快速降解，导致生物环境中的生物利用度差。为了解决此稳定性问题，我们使用姜黄素类化合物作为还原剂合成了姜黄素-银纳米颗粒（CUR-AgNP）复合物。在pH 7.4的磷酸盐缓冲液中孵育后，比较了单个姜黄素在CUR对照和CUR-AgNP复合物中的稳定性。有趣的是，与在CUR对照中观察到的49.6％降解相比，CUR-AgNP复合物中在4 h时姜黄素的初始降解仅为9.6％。在三种姜黄素类似物中，与姜黄素和脱甲氧基姜黄素相比，双去甲氧基姜黄素显示出更好的pH稳定性，而在CUR-AgNP复合物的情况下，所有三种姜黄素类化合物均表现出相同的降解模式。CUR-AgNP复合物的体外研究显示出对铜绿假单胞菌极好的抗菌性能。CUR-AgNP复合物还对MDA-MB231细胞表现出良好的细胞毒性作用。CUR-AgNP复合物的储存稳定性，在室温下以悬浮液形式保存（$〜$28 ${}^{\mathrm{Ø}}$C），通过测量其流体动力学尺寸和ζ电势进行测试。发现在储存340天后，粒径（Z平均）和zeta电位分别为65.5±1.1 nm和-22.9±0.2 mV，表明纳米颗粒悬浮液是稳定的。本研究获得的结果令人鼓舞并可以扩展以提高姜黄素在生物pH条件下的治疗效果。