• The Korean Journal of Food And Nutrition
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• v.32 no.1
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• pp.33-40
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• 2019

The purpose of this study was to evaluate the antioxidant and hepatocyte protective effects of guava (Psidium guajava L.) leaves cultivated in Korea. The contents of the total polyphenol of the extract was 271.57 mg gallic acid equivalent (GAE)/g residue. Antioxidant activities of leaf extract were evaluated by examining the free radical scavenging ability. 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and ${\alpha}-{\alpha}$-diphenyl-${\beta}$-picrylhydrazyl (DPPH) free radical scavenging activities of the extract were 1133.23 mg trolox equivalent antioxidant capacity (TEAC)/g residue and 721.68 mg TEAC/g residue, respectively. The hepatocyte protective effect of guava leaf extract was examined in HepG2 cells. Against tert-butyl hydroperoxide (TBHP), the viability of HepG2 cells were increased by the treatment of leaf extract. In addition, guava leaf extract led to the inhibition of reactive oxygen species (ROS) generated in HepG2 cells. The leaf extract increased the activity of glutathione (GSH), glutathione reductase (GR), and glutathione peroxidase (GPx) against oxidative stress. These results suggested that guava leaves might be regarded as a potential source natural antioxidant and a hepatoprotective material.

• Korean Journal of Food Science and Technology
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• v.38 no.5
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• pp.679-683
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• 2006

The effects of dried and fermented guava (Psidium guajava L.) leaf extracts on blood glucose levels were investigated in low-dose streptozotocin(STZ)-induced diabetic mice. Fermented guava leaf extract (500 mg/kg/day) significantly decreased the fasting blood glucose levels after 2-4 weeks of treatment and improved the impaired glucose tolerance in STZ-induced diabetic mice. On the other hand, dried guava leaf extract lowered the blood glucose levels and improved glucose tolerance two weeks after treatment, but exacerbated STZ-induced high blood glucose levels three and four weeks after treatment. Histological and immunohistochemical observation showed that fermented guava leaf extract treatment improved STZ-induced pancreatic beta-cell damage, but dried guava leaf extract did not affect the damage to the beta-cells. These results suggest that fermented guava (Psidium guajava L.) leaf extracts improve the hyperglycemia by protecting the pancreatic beta-cells hom damage in STZ-induced diabetic mice.

• Korean Journal of Plant Resources
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• v.21 no.5
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• pp.408-412
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• 2008

This research was designed to investigate the antioxidant activities and tyrosinase inhibitory effects of guava (Psidium guajava L.) leaf. Total phenol content was obtained from guava leaf extract of 19.0 (g/100g, D.W.). The crude extract exhibited significantly antioxidant activities (IC50value $102.5{\mu}g/ml$, free radical scavenging; $49.4{\mu}g/ml$, SOD like activity). The crude extract of guava leaf was fractionated into four partition layers; hexane (G-H), ethyl acetate (G-E), butanol (G-B) and water (G-W) layer. The extracts of G-E, G-B, G-W showed high radical scavenging activities of over 50% at $100{\mu}g/ml$. SOD like activities of G-E, G-B, G-W were revealed, as 81.8%, 84.7%, 65.3% at $100{\mu}g/ml$, while those of G-H did not showed the effectively. The crude extract of guava leaf showed high tyrosinase inhibitory effect as 60.8% at 1mg/ml, the measurement of G-E, G-B, G-W were 65.2%, 62.8%, 51.6% and that of G-H was not effective. These results indicate that useful bioactive substances exist in the guava leaf extracts, especially G-E, G-B. And the guava leaf has the potential of being developed into health related products.

• Nutrition Research and Practice
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• v.15 no.5
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• pp.568-578
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• 2021

BACKGROUND/OBJECTIVES: Psidium guajava L. (guava) leaves have been shown to exhibit hypoglycemic and antidiabetic effects in rodents. This study investigated the effects of guava leaf extract on adipogenesis, glucose uptake, and lipolysis of adipocytes to examine whether the antidiabetic properties are mediated through direct effects on adipocytes. MATERIALS/METHODS: 3T3-L1 cells were treated with 25, 50, 100 ㎍/mL of methanol extract from guava leaf extract (GLE) or 0.1% dimethyl sulfoxide as a control. Lipid accumulation was evaluated with Oil Red O Staining and AdipoRed assay. Immunoblotting was performed to measure the expression of adipogenic transcription factors, fatty acid synthase (FAS), and AMP-activated protein kinase (AMPK). Glucose uptake under basal or insulin-stimulated condition was measured using a glucose analog 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-2-deoxy-D-glucose. Lipolysis from fully differentiated adipocytes was measured by free fatty acids release into the culture medium in the presence or absence of epinephrine. RESULTS: Oil Red O staining and AdipoRed assay have shown that GLE treatment reduced lipid accumulation during adipocyte differentiation. Mitotic clonal expansion, an early essential event for adipocyte differentiation, was inhibited by GLE treatment. GLE inhibited the expression of transcription factors involved in adipocyte differentiation, such as peroxisome proliferator-activated receptor 𝛄 (PPAR𝛄), CCAAT/enhancer-binding protein α (C/EBPα), and sterol regulatory element-binding protein-1c (SREBP-1c). FAS expression was also decreased while the phosphorylation of AMPK was increased by GLE treatment. In addition, GLE increased insulin-induced glucose uptake into adipocytes. In lipid-filled mature adipocytes, GLE enhanced epinephrine-induced lipolysis but reduced basal lipolysis dose-dependently. CONCLUSIONS: The results show that GLE inhibits adipogenesis and improves adipocyte function by reducing basal lipolysis and increasing insulin-stimulated glucose uptake in adipocytes, which can be partly associated with antidiabetic effects of guava leaves.

• Korean Journal of Medicinal Crop Science
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• v.20 no.2
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• pp.94-100
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• 2012

Guava ($Psidium$ $guajava$) contain a great deal of polyphenol compound and work on the treatment of $Diabetes$ $mellitus$ effectively. In this study, the bioactivities of aqueous extract (GLEx) of guava leaf were investigated. Total phenolic contents of GLEx was 266.9 mg tan/g. The effects of GLEx on digestive enzymes, ${\alpha}$-amylase, maltase and sucrase were investigated. $IC_{50}$ values of GLEx against ${\alpha}$-amylase, maltase and sucrase were 0.65 mg/$m{\ell}$, 2.0 mg/$m{\ell}$ and 3.5 mg/$m{\ell}$ respectively. The effect of GLEx on oral glucose tolerance test (OGTT) was performed in normal ICR mouse, control (dstilled water) and GLEx (aqueous extract of Guava leaf) were co-administered orally with glucose, showed reducing effect on the blood glucose level. The guava is likely to useful for prevention or improvement of hyperglycemia by lowering the blood glucose level and inhibiting glycoside hydrolase activity.

• Fashion & Textile Research Journal
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• v.13 no.5
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• pp.778-789
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• 2011

The natural dyeing of silk fabrics with guava leaf extract was investigated. Mixed components of flavonoid and tannin seem to be the components of guava leaf extract. The temperature and time for dyeing of silk fabrics with guava leaf extract were $40^{\circ}C$ and $90^{\circ}C$ for eighty minutes, respectively. The dyeing equilibrium was shown at the fourth time of repeated dyeing. The highest K/S value was recorded at pH 3. Fe-mordanted fabrics showed the highest K/S value. High K/S values were shown in the post-mordanting of dyed fabrics at $40^{\circ}C$ and the pre-mordanting of dyed fabrics at $90^{\circ}C$. After repeated dyeing and mordanting, various color change occurred with mordant treatment. Surface colors were changed to YR color in alkaline water extract and to Y color in acidic water and ethanol extract, respectively. The washing fastness was level 3-4 for Sn-mordanted fabrics and level 4 for Fe-mordanted fabrics, and the dry cleaning fastness also showed very excellent result with level 4-5. The rubbing fastness was satisfactory with level 3-4. The light fastness was above level 4 only when Fe-mordanting was conducted, and the rest of dyed fabrics was not fast enough. In the antibacterial activity, the powder of guva leaf extract showed 99.9% of high antibacterial activity and Staphylococcus aureus showed 99.6% in dyed fabric. All dyed fabrics showed higher deodorization and UV protection rate than control fabric.

• The Korean Journal of Food And Nutrition
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• v.25 no.2
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• pp.317-323
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• 2012

We investigated the quality characteristics of cookies prepared after the addition of various concentration of used guava leaf powder(0%, 1%, 3%, 5%, all w/w) as a substitute for flour. In this study, as guava leaf powder concentration rose, there was a decrease in the water content level. In addition, color, spread factor, hardness and sensory evaluation of the cookies were examined. The results showed that with an increase in guava leaf powder concentration, the L value decreased significantly, while the values for a and b of cookies increased when more guava leaf power was added to cookies. The spread factor of cookies decreased, but the hardness of cookies increased significantly, as guava leaf powder concentration increased. Cookies containing 0% and 3% of guava leaf powder showed a similar sensory evaluation score in terms of color, taste and flavor of the cookies. In the case of texture and overall consumer acceptability, cookies with 3% of guava leaf powder showed the highest score.

• Microbiology and Biotechnology Letters
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• v.47 no.1
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• pp.43-53
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• 2019

The anticancer activity of guava (Psidium guajava L.) leaf extract (GLE) occurs via the induction of apoptosis in cancer cells. However, the mechanism behind GLE-induced apoptosis in the human hepatocellular carcinoma cell line HepG2 remains unclear. In the present study, we investigated the apoptotic effects and mechanism of action of GLE in cultured HepG2 cells. The results showed that GLE induced reactive oxygen species (ROS) synthesis and disrupted the mitochondrial membrane potential (${\Delta}{\Psi}m$). Moreover, GLE increased the expression of apoptotic pathway proteins, such as the cleaved forms of caspase-3, -8, and -9; the translocation of Bax and cytochrome c (cyt-c) from the mitochondria to the cytosol; and the downregulation of Bcl-2. In addition, p53 protein expression was increased upon GLE treatment. These observations indicate that the GLE-induced apoptosis in HepG2 cells is mediated by mitochondrial ROS generation, followed by caspase activation and cyt-c release, suggesting that GLE may be a promising candidate for the development of novel drugs for the treatment of liver cancers.

• Fashion & Textile Research Journal
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• v.14 no.2
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• pp.320-330
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• 2012

The natural dyeing of cotton fabrics with guava leaf extract was investigated. The temperature and time of dyeing are $40^{\circ}C$ and $90^{\circ}C$ for eighty minutes, respectively. In addition, the dyebath has been set at pH 5. Sn pre-mordanted fabrics showed the highest K/S value. Regardless of dyeing temperature, K/S values were high when Al, Cu, Fe-mordanted fabrics were dyed in post-mordanting and Sn-mordanted fabrics were dyed in pre-mordanting. The K/S value of dyeing fabrics could be increased with repetitive dyeing and mordanting. Compared to untreated dyed fabrics, the K/ S values of fabrics which had been treated with soybean milk, chitosan and gall nut tannin were increased. The changed surface colors of fabrics that were treated with soybean milk, chitosan and gall nut tannin were Y, YR and achromatic colors. Fabrics dyed with alkaline water extract showed reddish color. Sn-mordanted fabrics dyed with acidic water extract showed vivid yellowish color, and Cu-mordanted fabrics dyed with ethanol extract showed yellowish green color. In case of Sn-mordanted fabrics, the washing fastness was level 4. The dry cleaning fastness also showed very excellent result with level 4-5. The rubbing fastness was better in dry rubbing than in wet rubbing of the fabrics. For the light fastness, all dyed fabrics showed low fastness. For antibacterial activity, the powder of guava leaf extract and the dyed fabrics with guava leaf extract showed 99.9% of high antibacterial activity. All dyed fabrics showed higher deodorization and UV protection rate than control fabric.

• Fashion & Textile Research Journal
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• v.14 no.5
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• pp.866-877
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• 2012

The natural dyeing of hanji cotton fabrics with guava leaf extract was investigated. The temperature and time of dyeing were $40^{\circ}C$ and $90^{\circ}C$ for eighty minutes, respectively. In addition, the dyebath has been set at pH 5. Sn pre-mordanted fabrics showed the highest K/S value. Regardless of dyeing temperature, K/S values were high when Al, Cu, Fe-mordanted fabrics were dyed in post-mordanting and Sn-mordanted fabrics in pre-mordanting. The dyeing equilibrium was shown at the fourth time of repeated dyeing. In the processing of hanji cotton fabrics, K/S value was high when hanji cotton fabric was treated with soybean milk at $90^{\circ}C$. Similar K/S value of dyeing was shown when fabrics were processed with chitosan, regardless of dyeing temperature. High K/S value of dyeing was seen when fabrics processed with gallnut tannin at 40. Fabrics dyed with acidic water extract showed yellowish color. Fabrics dyed with alkaline water extract showed reddish color, and fabrics dyed with ethanol extract showed greenish yellow color. In case of Sn-mordanted fabrics, the washing fastness level was between 3 to 4, and other dyed fabrics showed low fastness. The dry cleaning fastness also showed very excellent result with level 4-5. The rubbing fastness of the fabrics was better in dry rubbing than in wet rubbing. For the light fastness, all dyed fabrics showed low fastness. For antibacterial activity, the dyed fabrics with guava leaf extract showed 99.9% of high antibacterial activity. Hanji cotton fabric maintained certain deodorization in the state of raw fabric. All dyed fabrics showed higher UV protection rate than control fabric.