Stability of Bioactive Compounds and Antioxidant Activities of Kenaf Seed Oil-in-Water Nanoemulsions under Different Storage Temperatures

Kenaf seed oil-in-water nanoemulsions (NANO) stabilized by sodium caseinate (SC), beta-cyclodextrin (β-CD), and Tween 20 (T20) have been optimized and shown to improve in vitro bioaccessibility and physicochemical stability in the previous study. The main objective of this study was to evaluate the stability of bioactive compounds and antioxidants in the NANO during storage at different temperatures (4 °C, 25 °C, and 40 °C). An evaluation of the antioxidant activities of each emulsifier showed that SC had good scavenging capability with 97.6% ABTS radical scavenging activity. Therefore, SC which was used as one of the main emulsifiers could further enhanced the antioxidant activity of NANO. At week 8 of storage, NANO that stored at 4 °C had maintained the best bioactive compounds stability and antioxidant activities with 90% retention of vitamin E and 65% retention of phytosterols. These results suggested that 4 °C would be the most suitable storage temperature for NANO containing naturally present vitamin E and phytosterols. From the accelerated storage results at 40 °C, NANO containing vitamin E and phytosterols had maintained half of its initial concentration until week 4 and week 2 of storage, which is equivalent to 16 weeks and 8 weeks of storage at room temperature, respectively.

PRACTICAL APPLICATION

The results of this study provide a better understanding on the stability of bioactive compounds and antioxidant activities in oil-in-water nanoemulsions that stabilized by similar ternary emulsifiers during storage at different temperatures. In addition, this study could be used as a predictive model to estimate the shelf life of bioactive compounds encapsulated in the form of nanoemulsions.

Effect of Emulsification Method and Particle Size on the Rate of in vivo Oral Bioavailability of Kenaf (Hibiscus cannabinus L.) Seed Oil

Kenaf (Hibiscus cannabinus L.) seed oil-in-water nanoemulsions stabilized by complexation of beta-cyclodextrin with sodium caseinate and Tween 20 have been shown to have higher bioaccessibility of vitamin E and total phenolic content than nonemulsified kenaf seed oil in the previous in vitro gastrointestinal digestion study. However, its oral bioavailability was unknown. Therefore, the aim of this study was to evaluate the rate of in vivo oral bioavailability of kenaf seed oil-in-water nanoemulsions in comparison with nonemulsified kenaf seed oil and kenaf seed oil macroemulsions during the 180 min of gastrointestinal digestion. Kenaf seed oil macroemulsions were produced by using conventional method. Kenaf seed oil-in-water nanoemulsions had shown improvement in the rate of absorption. At 180 min of digestion time, the total α-tocopherol bioavailability of kenaf seed oil nanoemulsions was increased by 1.7- and 1.4-fold, compared to kenaf seed oil and macroemulsion, respectively. Kenaf seed oil-in-water nanoemulsions were stable in considerably wide range of pH (>5 and <3), suggesting that it can be fortified into beverages within this pH range PRACTICAL APPLICATION: The production of kenaf seed oil-in-water nanoemulsions had provided a delivery system to encapsulate the kenaf seed oil, as well as enhanced the bioaccessibility and bioavailability of kenaf seed oil. Therefore, kenaf seed oil-in-water nanoemulsions exhibit a great potential application in nutraceutical fields.

Improvement of gastroprotective and anti-ulcer effect of kenaf seed oil-in-water nanoemulsions in rats

Kenaf seed oil-in-water nanoemulsions (KSON) and kenaf seed oil-in-water macroemulsions were produced to access their gastroprotective effect against indomethacin- and ethanol-induced ulcers in comparison with non-emulsified kenaf seed oil (KSO). Emulsifier mixture (EM) that used to emulsify KSO was also included in the study. Ulcer index, stomach tissue oxidative status, and histopathological changes in indomethacin-induced and ethanol-induced ulcer models were both evaluated. KSON had demonstrated good gastroprotective effect against both ulcer models than non-emulsified KSO and KSOM. In addition, the gastroprotective effect of KSON was comparable to the standard drug, Omeprazole. EM also exhibited gastroprotective effect, especially in indomethacin-induced ulcers. This may be attributed to its high antioxidant activity and cytoprotective effect of sodium caseinate contained in the EM. Results supported that KSON enhanced the bioavailability of native KSO; therefore it offers gastroprotective effect for the prevention of gastric ulceration as a natural alternative to the synthetic drug.

Hypocholesterolemic Effects of Kenaf Seed Oil, Macroemulsion, and Nanoemulsion in High-Cholesterol Diet Induced Rats

This study aimed to evaluate the effect of kenaf seed oil (KSO), kenaf seed oil-in-water macroemulsion (KSOM), kenaf seed oil-in-water nanoemulsions (KSON), and emulsifier mixtures (EM) on serum lipid profile, liver oxidative status, and histopathological changes in high-cholesterol fed rats. Stability and characteristic of KSOM and KSON were carried out prior to in vivo study. Forty-two Sprague-Dawley rats were divided into 7 groups (6 rats each) and induced hypercholesterolemia by feeding high cholesterol diet (HCD) for 14 days prior to treatments. Different treatments were introduced on day 15 to 29 while supplemented with HCD and removal of HCD during treatment on day 30 to 43, except for HCD group. Body weight and serum lipid profiles were measured at 3 different points: after hypercholesterolemia was induced, on day 29, and at the end of the experiment. Relative liver weight, atherogenic index, coronary risk index, and fecal total bile acids were also determined at the end of experiment. KSON showed significantly higher stability than KSOM and FTIR exhibited good encapsulation of KSO after 1.5 years of storage. Serum total cholesterol, low density lipoprotein cholesterol, lipid peroxidation levels in HCD group without treatment were significantly higher compared to normal control group and all treatment groups. All samples demonstrated hypocholesterolemic effect, but KSON exhibited higher efficiency in cholesterol-lowering properties, weight control and decreased liver fat as confirmed by histopathological evaluation. The overall results revealed that the efficacy of different treatments was in descending order of KSON, KSO, KSOM, and EM.

PRACTICAL APPLICATION

Kenaf seed oil-in-water nanoemulsion (KSON) has the potential to be used as a natural alternative to the synthetic hypocholesterolemic drug in the future. However, larger sample size and clinical trial are needed to confirm on this potential application. In addition, treatment with KSON was suggested to prevent cardiovascular disease and fatty liver.