Oxidative stress, caused by the excessive production of reactive oxygen species (ROS), results in cellular damage. Therefore, functional materials with antioxidant properties are necessary to maintain redox balance. Turmeric leaves (Curcuma longa L. leaves; TL) are known to have antioxidant properties, including 2,2-Diphenyl-1-picrylhydrazyl (DPPH), 2,2′-Azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS), and Hydrogen peroxide (H₂O₂) radical scavenging activity in several studies. The antioxidant effects of TL come from distinct bioactive compounds, such as curcumin, total phenolic compounds, and flavonoids. Therefore, in this study, the antioxidant effects of a water extract of TL (TLE) against H₂O₂ treatment were assessed in vitro Vero cells and in vivo zebrafish models. The intracellular ROS generation and the proportion of sub-G1 phase cells were evaluated in H₂O₂- or/and TLE-treated Vero cells to measure the antioxidant activity of TLE. TLE showed outstanding intracellular ROS scavenging activity and significantly decreased the proportion of cells in the sub-G1 phase in a dose-dependent manner. Furthermore, cell death, ROS generation, and lipid peroxidation in the H₂O₂-treated zebrafish model were attenuated as a consequence of TLE treatment. Collectively, the results from this study suggested that TLE may be an alternative material to relieve ROS generation through its antioxidant properties or a suitable material for the application in a functional food industry.

Curcuma longa L. (turmeric) has been used as a functional food material, but other parts of it such as leaves are wasted as a byproduct. This work concentrated on developing turmeric leaves as a functional food material by establishing its optimal extraction condition. Response surface methodology was applied to optimize turmeric leaf extraction conditions. Turmeric leaves were pulled out with water and ethanol (10, 30, and 50%). Then, total phenolic compound content, total flavonoid content, and radical-scavenging activity of each extract were quantified to confirm the optimal extracting solvent. According to the results, water was the most efficient solvent to extract antioxidant contents such as total phenolic compounds (3.65 ± 0.02 mg GAE/g) and flavonoids (4.99 ± 0.17 mg QCE/g) content. Radical-scavenging activity was also higher in water extract compared with others such as DPPH (51.10 ± 2.29%), H₂O₂ (25.39 ± 2.69%), and ABTS (91.08 ± 0.15%). Central composite design was applied to confirm the effect of independent variables such as temperature (X₁) and time (X₂) to the yield (Y₁). After conducting experiments, the extraction condition was established as 150 min with 1 : 25 ratio at 85°C with a 15.58% yield. Proximate compositions of the extract were determined to suggest background data for further research. In conclusion, this study confirmed the antioxidant property of turmeric leaves and developed the optimal extraction condition of the leaves to promote its application in food industry as a new food source.

Advanced glycation end-products (AGEs) such as methylglyoxal (MGO) play a vital role in the pathogenesis of nephropathy, a diabetic complication. In the present study, we evaluated the anti-glycation and renal protective properties of Ishige okamurae extract (IOE) against AGE-induced oxidative stress. HPLC analysis confirmed that bioactive phlorotannins such as diphlorethohydroxycarmalol and ishophloroglucin A are predominantly present in IOE. IOE showed strong anti-glycation activities via inhibition of AGE formation, inhibition of AGE–protein cross-linking, and breaking of AGE–protein cross-links. In addition, in vitro studies using mesangial cells demonstrated that IOE effectively suppressed intracellular reactive oxygen species production, intracellular MGO accumulation, and apoptotic cell death by MGO-induced oxidative stress, in addition to regulating the expression of proteins involved in the receptor for AGEs and nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response elements (ARE) signaling pathways. Therefore, IOE can serve as a natural therapeutic agent for the management of AGE-related nephropathy.

본 연구에서는 제주도에서 자생하는 홍조류인 우뭇가사리 (Gelidium amansii) 70% (v/v) 에탄올 추출물(GAE)의 항당화 (anti-glycation) 효능 및 최종당화산물로 유도되는 당뇨병성 합병증 중 하나인 신장병증(nephropathy)에 대한 예방 효과를 평가하였다. GAE는 모든 처리 농도(1, 5, 및 20 μg/mL)에서 BSA, glucose, 및 fructose로 인해 생성되는 최종당화산물을 유의적으로 감소시키는 것을 확인하였다. 또한 GAE의 전처리는 최종당화산물과 콜라겐 단백질 사이의 교차결합 형성을 유의적으로 억제 시켰으며, 최종당화산물과 콜라겐 단백질 사이에 이미 형성된 비가역적 교차결합에 GAE를 처리하였을 때 매우 효과적으로 절단하는 효능을 가지고 있음을 확인하였다. GAE의 신장 보호 효과를 평가하기 위해 mouse glomerular mesangial 세포 보호 효능을 평가한 결과 최종당화산물의 전구체인 MGO로 유도된 세포 독성으로부터 신장 세포를 보호하는 효과를 나타내었다. 이러한 효과는 GAE의 전처리가 MGO로 인해 증가하는 신장 세포 내 ROS 생성 억제, 세포 내 최종당화산물 축적 감소, 및 세포 내 MGO 축적 감소를 통해 신장 세포의 apoptosis를 억제하기 때문인 것을 확인하였다. 본 연구를 통해 GAE는 합성 당뇨합병증 치료제로 알려진 아 미노구아니딘과 유사한 수준의 효능을 가지고 있음을 확인하였다. 그러므로 우뭇가사리는 최종당화산물로 인해 유도되는 당뇨병성 신병증을 예방 및 치료하는 효과를 가지고 있는 것으로 보이며, 부작용 위험이 낮은 천연 당뇨합병증 치료제로 개발 잠재력이 높은 것으로 사료된다.