Sudachi Peel Research Articles

Effect of Mixing Ratios of Sudachi Peel on the Stability of Anaerobic Co-digestion of Rural Sewage Sludge, Kitchen Garbage and Sudachi Peel

Effect of Mixing Ratios of Sudachi Peel on the Stability of Anaerobic Co-digestion of Rural Sewage Sludge, Kitchen Garbage and Sudachi Peel

Sudachi peel extract powder including the polymethoxylated flavone sudachitin improves visceral fat content in individuals at risk for developing diabetes.

In vitro and animal studies have indicated that extracts from the peel of the Japanese Citrus sudachi, including sudachitin, ameliorate hyperlipidemia and reduce obesity. Sudachitin, a polymethoxylated flavone, has been reported as having favorable effects on lipid and glucose metabolism but results from clinical trials have been inconsistent. The aim of this study was to determine the effect of consuming capsules of sudachi peel extract powder on visceral fat in Japanese men and women in a randomized controlled trial. This was a 12‐week randomized, double‐blind, placebo‐controlled trial involving 41 participants aged 30–65 years with BMI 23–30 kg/m2, randomly allocated to receive either sudachi peel extract powder (sudachitin 4.9 mg/day, n = 21) or placebo (n = 20) of identical appearance. The primary outcome measure was visceral fat mass, assessed during intervention. Thirty‐eight of the 41 subjects completed the protocol. Compared with placebo, sudachi peel extract powder significantly reduced the ratio of visceral fat to subcutaneous fat, and moderately reduced waist circumference, a metabolic syndrome marker. Glycemic control and lipid profile were not changed significantly in these subjects. Consumption of capsules of sudachi peel extract powder favorably improves the ratio of visceral fat to subcutaneous fat in individuals at risk for developing diabetes, especially in individuals with large visceral fat area, while not adversely affecting glycemic control.

Citrus sudachi Peel Extract Suppresses Cell Proliferation and Promotes the Differentiation of Keratinocytes through Inhibition of the EGFR-ERK Signaling Pathway.

Citrus sudachi is a well-known fruit in Tokushima Prefecture, Japan, and its peels are rich in phytochemicals, including phenolic compounds. Although it is expected that the extract of the C. sudachi peel elicits various beneficial physiological activities, the effect on the skin has not been investigated. In this study, we report that the aqueous extract from the peel of C. sudachi suppresses cell proliferation of the immortalized human keratinocyte cell line, HaCaT, and primary normal human epidermal keratinocytes. The extract of C. sudachi peel suppressed epidermal growth factor (EGF)-induced EGF receptor activation and tumor necrosis factor (TNF)-α-induced extracellular regulated kinase (ERK) 1/2 activation, which suggests that the extract exerts its inhibitory effect through inhibition of both the EGF receptor (EGFR) and its downstream molecules. Additionally, the extract of C. sudachi peel potentiated calcium-induced keratinocyte differentiation. These results suggest that the extract of C. sudachi peel may have beneficial effects against skin diseases that are characterized by hyperproliferation of epidermal keratinocytes, such as those seen in psoriasis and in cutaneous squamous cell carcinoma.

Metabolic beneficial effects of Citrus Sudachi

Sudachi (Citrus Sudachi) is a sour fruit and is a popular seasoning for Japanese dishes, Washoku. It can grow only in Tokushima and the surrounding areas for some reason, and therefore, Sudachi is a specialty of Tokushima prefecture in Japan. We usually use only its juice, and the size of the fruit is so small that a huge amount of pomace has been an industrial problem of the region. Therefore, we undertook exploratory studies of the Sudachi peel in terms of health promotion with making a kind of collaborative consortium for the study of acid citruses. Our recent activities on Sudachi research including the consortium were shared and discussed in the symposium, and the metabolic effects of Sudachi peel will be briefly introduced in the current manuscript.

Improvement of Lipid Metabolism in Mice Fed a High-Fat Diet Treated with Sudachitin and Development of Sudachi Peel Extract Powder

Sudachi, Citrus sudachi, is a major local food in Tokushima Prefecture, and over 98% of this fruit is produced in Tokushima Prefecture. After juice is extracted from sudachi, sudachi peer is not used effectively. Sudachitin, a polymethoxylated flavone is isolated from sudachi peer, and its structure is similar to nobiletin, which possesses anti-inflammatory and anti-obesity actions. First, we evaluated the effect of sudachitin on lipid and energy metabolism in mice fed a high-fat diet. C57BL/6J mice were fed a high-fat diet treated with 5mg/kg/day sudachitin orally for 12 weeks. The mice treated with sudachitin showed significantly decreased body weight gain, body fat and viscera fat compared to that of mice fed a high-fat diet. Moreover, sudachitin improved glucose intolerance and insulin resistance in these mice. We concluded that sudachitin may improve metabolic syndrome by enhancing energy metabolism. Purified sudachitin cannot be used as a food ingredient because of the possibility of side effects and it is too expensive for clinical use at present. Therefore, we tried to produce a sudachi powder which contained sudachitin at high concentration from the dried sudachi peer containing a low amount of sudachitin. It is possible to adjust the content step-by-step from 1% to 80%. We also evaluated the function of sudachi peer extract powder using an animal model of obesity. The mice treated with sudachi peer extract powder showed significantly decreased body weight gain compared to that of mice fed a high-fat diet.

Methanol extraction fraction from Citrus Sudachi peel exerts lipid reducing effects in cultured cells.

Ectopic fat accumulation is associated with insulin resistance and type 2 diabetes mellitus. Citrus sudachi is an evergreen tree that is found mainly in Tokushima Prefecture in Japan. Previously, it was demonstrated that Citrus sudachi could inhibit the rising trend of blood glucose and fatty acid in human subjects. In the current study, we illustrated the function of methanol extracts from sudachi peel and investigated the mechanism of this effect. We got the five kinds of methanol extracts by using diaion HP-20, and those were named by hydrophobicity from M-F1 to M-F5. Among the 5 kinds of sudachi methanol extracts, only M-F4 significantly decreased the intracellular triglyceride of C2C12 cells. It augmented the AMPK activity and increased the transcription of PPARα and its downstream targets CPT-1b and UCP2. In conclusion, M-F4 improved the lipid metabolism possibly through AMPK, PPARα and their downstream targets like CPT-1b and UCP2. Furthermore, this extract may be useful for preventing obesity and diabetes related diseases. J. Med. Invest. 65:225-230, August, 2018.

Extracts of citrus Sudachi peel attenuate body weight gain in C57BL/6 mice fed a high-fat diet.

Citrus Sudachi is the special local product of Tokushima Prefecture, and over 98% of Sudachi consumed in Japan every year is produced in Tokushima Prefecture. In this study, we evaluated the function of sudachi peel extract (SPE) using an animal model of obesity. C57BL/6 mice were fed a high-fat diet containing 1% SPE powder. Treatment with SPE significantly decreased body weight compared to that of mice fed a high-fat diet. A significant difference in body weight was observed between the control and SPE groups from 7 weeks after the start of the experiment, the significant difference continued until the end of the 14-week experiment. Reduction of blood glucose levels following insulin administration in SPE-treated mice was grater than that in control mice. Determination of mRNA expression in adipose tissue showed that the expression level of TNF-α in the SPE group was significantly decreased compared to that on the control group. These results suggest that SPE potentially has the ability to attenuate body weight gain. J. Med. Invest. 64: 20-23, February, 2017.

Efficacy and safety of Citrus sudachi peel in obese adults: A randomized, double-blind, pilot study

Objective: This study was undertaken to explore the efficacy and safety of Citrus sudachi peel for metabolic risk factors in obese male and female adults.Background: Citrus sudachi Hort. ex Shirai (Rutaceae), called “sudachi”, is a small, round, green citrus fruit that is mainly cultivated in Tokushima Prefecture in Japan. Our group reported that Citrus sudachi peel powder improved glucose tolerance and dyslipidemia in Zucher-fatty rats and reduced hyperglycemia and hypertriglyceridemia in GK diabetic rats.Materials and Methods: We conducted a randomized, double-blind, placebo-controlled trial in 40 participants with abdominal obesity and metabolic risk factors including hypertension, impaired glucose tolerance and elevated triglyceride levels. Participants were randomized to receive either tablets that contained 1.3 g dried Citrus sudachi peel powder or placebo tablets for 12 weeks. The sudachi peel group included 14 males and 5 females with a mean age of 54.5 years, and the placebo group included 18 males and 2 females with a mean age of 51.9 years. Results: Physical status including body weight, waist circumference and blood pressure and laboratory markers including metabolic parameters were not different at any observation point between the two groups. However, among participants with serum triglyceride levels of more than 120 mg/dl, body weight, waist circumference and serum triglyceride levels were significantly decreased at several observation points after the start of treatment in the sudachi peel group but not in the placebo group. No serious adverse events were observed in the sudachi peel group. Conclusions: Citrus sudachi peel has the potential effect to safely improve abdominal obesity and lower serum levels of TG in obese individuals with hypertriglyceridemia. A large-scale randomized, double-blind clinical study targeting subjects with both abdominal obesity and high TG levels is needed to confirm the metabolic effects of Citrus sudachi peel.Trial registration: UMIN Clinical Trials Registry (UMIN-CTR) UMIN000002682. Accession number of the Ethics Committee for Clinical Trials of Food in Tokushima University Hospital is F5.Key words: health functional food, anti-obesity, triglyceride

Optical Isomers and Odor Thresholds of Volatile Constituents in Citrus sudachi.

The enantioselective analysis of the volatile components in Citrus sudachi peel oils was achieved using an enantioselective capillary gas chromatography (enantio-cGC) with α- and β-cyclodextrin columns. The two isomers of linalool and α-pinene showed highly significant differences in both odor detection thresholds and odor qualities. The other investigated compounds also differed either in the odor intensities or in the odor qualities. According to limited odor units (ratio of the concentration of each component to the odor threshold), (3S)-(+)-linalool, (3R)-(—)-linalool, octanal, (4R)-(+)-limonene, (1R,5R)-(+)-α-pinene, p-cymene, γ-terpinene, myrcene, 1,8-cineole, (3R)-(+)-citronellal, decanal, α-phellandrene and dodecanal contributed to the Citrus sudachi aroma.