Kumju Youn

p-Coumaric Acid and Ursolic Acid from Corni fructus Attenuated β-Amyloid25–35-Induced Toxicity through Regulation of the NF-κB Signaling Pathway in PC12 Cells

Neuroinflammatory responses induced by amyloid-beta peptide (Aβ) are important causes in the pathogenesis of Alzheimers disease (AD). Blockade of Aβ has emerged as a possible therapeutic approach to control the onset of AD. This study investigated the neuroprotective effects and molecular mechanisms of p-coumaric acid (p-CA) and ursolic acid (UA) from Corni fructus against Aβ(25-35)-induced toxicity in PC12 cells. p-CA and UA significantly inhibited the expression of iNOS and COX-2 in Aβ(25-35)-injured PC12 cells. Blockade of nuclear translocation of the p65 subunit of nuclear factor κB (NF-κB) and phosphorylation of IκB-α was also observed after p-CA and UA treatment. For the upstream kinases, UA exclusively reduced ERK1/2, p-38, and JNK phosphorylation, but p-CA suppressed ERK1/2 and JNK phosphorylation. Both compounds comprehensively inhibited NF-κB activity, but possibly with different upstream pathways. The results provide new insight into the pharmacological modes of p-CA and UA and their potential therapeutic application to AD.

In vitro BACE1 inhibitory activity of geraniin and corilagin from Geranium thunbergii.

Generation of amyloid β peptide through the proteolytic process of amyloid precursor protein by β-secretase and γ-secretase is a main casual factor of Alzheimers disease, since amyloid β peptide is a major and crucial component of senile plaques in Alzheimers disease brains. In the process of searching for β-secretase inhibitors from natural resources, the EtOAc soluble fraction of Geranium thunbergii exhibited significant β-secretase inhibitory activity. Two compounds, geraniin and corilagin, isolated from the most active EtOAc fraction of G. thunbergii, exhibited predominant inhibition against β-secretase with IC₅₀ values of 4.0 × 10⁻⁶ M and 3.4 × 10⁻⁵ M, respectively. Dixon plot of geraniin and corilagin demonstrated that the β-secretase inhibition was noncompetitive with the substrate, thus clearly suggesting that these compounds might bind either to the β-secretase subsites or to another regulatory domain with Ki values of 2.8 × 10⁻⁶ M and 7.9 × 10⁻⁵ M, respectively. Both compounds exhibited no significant inhibition against α-secretase and other serine proteases including trypsin and chymotrypsin, showing that they were relatively specific and selective inhibitors of β-secretase. These novel findings suggest that geraniin and corilagin from G. thunbergii may be effective therapeutic agents for further drug development in Alzheimers disease.

Inhibitory Effects of Key Compounds Isolated from Corni fructus on BACE1 Activity

Progressive cerebral deposition of Aβ in the brain is a seminal event in the pathogenesis of Alzheimers disease (AD). Aβ is generated from the amyloid precursor protein (APP) by proteolytic processing of β‐secretase (BACE1) and γ‐secretase. Consequently, BACE1, a key enzyme in the production of Aβ, is a prime target for therapeutic intervention in AD. In the course of screening for natural BACE1 inhibitors from Corni fructus, the ethyl acetate (EtOAc) fraction showed significant inhibitory activity against BACE1. By activity guided purification, three compounds of BACE1 inhibitors p‐coumaric acid, gallic acid and ursolic acid were isolated from Corni fructus EtOAc fraction. All isolated compounds suppressed BACE1 in a dose dependent manner. p‐Coumaric acid, in particular, exhibited significant inhibitory activity against BACE1 with 9.0 × 10‐5 m and a Ki value of 1.9 × 10‐6 m. Also this compound was non‐competitive with a substrate in the Dixon plot, suggesting that it might bind either to the β‐secretase subsite or to another regulatory site. All compounds showed no significant attenuation of TACE (α‐secretase) and other serine proteases such as chymotrypsin and trypsin, demonstrating that they were relatively selective and specific inhibitors of BACE1. These novel findings suggest that Corni fructus contains biologically active components that may be used to attenuate the progression and/or prevention of Alzheimers disease. Copyright

Oleic acid and linoleic acid from Tenebrio molitor larvae inhibit BACE1 activity in vitro: molecular docking studies.

In our ongoing research to find therapeutic compounds for Alzheimers disease (AD) from natural resources, the inhibitory activity of the BACE1 enzyme by Tenebrio molitor larvae and its major compounds were evaluated. The T. molitor larvae extract and its fractions exhibited strong BACE1 suppression. The major components of hexane fraction possessing both high yield and strong BACE1 inhibition were determined by thin layer chromatography, gas chromatography, and nuclear magnetic resonance analysis. A remarkable composition of unsaturated long chain fatty acids, including oleic acid and linoleic acid, were identified. Oleic acid, in particular, noncompetitively attenuated BACE1 activity with a half-maximal inhibitory concentration (IC₅₀) value of 61.31 μM and Ki value of 34.3 μM. Furthermore, the fatty acids were stably interacted with BACE1 at different allosteric sites of the enzyme bound with the OH of CYS319 and the NH₃ of TYR320 for oleic acid and with the C=O group of GLN304 for linoleic acid. Here, we first revealed novel pharmacophore features of oleic acids and linoleic acid to BACE1 by in silico docking studies. The present findings would clearly suggest potential guidelines for designing novel BACE1 selective inhibitors.

Fatty Acid and Volatile Oil Compositions of Allomyrina dichotoma Larvae

Thirty-two different volatile oils were identified from Allomyrina dichotoma (A. dichotoma) larvae by gas chromatography/mass spectrometry (GC/MS). The major volatile components were 2,2,4-trimethyl-3-carboxyisopropyl pentanoic acid isobutyl ester (5.83%), phenol,2,6-bis(a,a-dimethyl ethyl)-4-(1-methyl-1-phenylethyl) (5.72%), heptacosane (5.49%) and phenol,2,4-bis(1-methyl-1-phenylethyl) (5.47%). The composition of the fatty acids in A. dichotoma larvae was also determined by gas chromatography (GC) and fourteen constituents were identified. Oleic acid (19.13%) was the most abundant fatty acid followed by palmitic acid (12.52%), palmitoleic acid (3.71%) and linoleic acid (2.08%) in 100 g of A. dichotoma larvae on a dry weight basis. The quantity of unsaturated fatty acids (64.00%) were higher than that of saturated ones (36.00%). The predominant fatty acids in A. dichotoma consist of monounsaturated fatty acid (MUFA, 57.70%) such as oleic acid, myristoleic acid and palmitoleic acid, followed by saturated fatty acids (36.00%) and polyunsaturated fatty acids (PUFA, 6.50%). In particular, the presence of essential fatty acids, such as linoleic (5.30%) and linolenic acid (0.40%) give A. dichotoma larvae considerable nutritional and functional value and it may be a useful source for food and/or industrial utilization.

β-Secretase (BACE1) inhibitory property of loganin isolated from Corni fructus

In the course of searching for anti-dementia agents from natural products, loganin isolated from EtOAc fraction of Corni fructus possessed specific inhibitory activity against β-secretase (BACE1) with 9.2 × 10−5 M and Ki value of 5.5 × 10−5 M. Loganin exhibited less inhibitory activity to α-secretase (TACE) and other serine proteases exhibiting that it was a relatively specific inhibitor of BACE1. These novel findings suggest that loganin may be used to attenuate the progression and/or prevention of Alzheimers disease.

Fatty Acid Composition and Volatile Constituents of Protaetia brevitarsis Larvae.

A total of 48 different volatile oils were identified form P. brevitarsis larvae by gas chromatography/mass spectrometry (GC/MS). Acids (48.67%) were detected as the major group in P. brevitarsis larvae comprising the largest proportion of the volatile compounds, followed by esters (19.84%), hydrocarbons (18.90%), alcohols (8.37%), miscellaneous (1.71%), aldehydes (1.35%) and terpenes (1.16%). The major volatile constituents were 9-hexadecenoic acid (16.75%), 6-octadecenoic acid (14.88%) and n-hexadecanoic acid (11.06%). The composition of fatty acid was also determined by GC analysis and 16 fatty acids were identified. The predominant fatty acids were oleic acid (C18:1, 64.24%) followed by palmitic acid (C16:0, 15.89%), palmitoleic acid (C16:1, 10.43%) and linoleic acid (C18:2, 4.69%) constituting more than 95% of total fatty acids. The distinguished characteristic of the fatty acid profile of P. brevitarsis larvae was the high proportion of unsaturated fatty acid (80.54% of total fatty acids) versus saturated fatty acids (19.46% of total fatty acids). Furthermore, small but significant amounts of linoleic, linolenic and γ-linolenic acids bestow P. brevitarsis larvae with considerable nutritional value. The novel findings of the present study provide a scientific basis for the comprehensive utilization of the insect as a nutritionally promising food source and a possibility for more effective utilization.

Effects of solvent fractions of Allomyrina dichotoma larvae through the inhibition of in vitro BACE1 and β‐amyloid(25–35)‐induced toxicity in rat pheochromocytoma PC12 cells

Amyloid‐β peptide (Aβ) generation initiated by β‐site amyloid precursor protein cleaving enzyme 1 BACE1 is a critical cause of Alzheimers disease. In the course of our ongoing investigation of natural anti‐dementia resources, the ethyl acetate (EtOAc) fraction exerted strong BACE1‐specific inhibition with the half maximal inhibitory concentration (IC50) value of 9.2 × 10−5 μg/mL. Furthermore, Aβ(25–35)‐induced cell death was predominantly prevented by the EtOAc fraction of Allomyrina dichotoma larvae through diminishing of cellular oxidative stress and attenuating apoptosis by inhibiting caspase‐3 activity. Taken together, the present study demonstrated that A. dichotoma larvae possess novel neuroprotective properties not only via the selective and specific inhibition of BACE1 activity but also through the alleviation of Aβ(25–35)‐induced toxicity, which may raise the possibility of therapeutic application of A. dichotoma larvae for preventing and/or treating dementia.

Polymethoxyflavones: Novel β-Secretase (BACE1) Inhibitors from Citrus Peels

Beta-site amyloid precursor protein (APP) cleaving enzyme1 (BACE1) catalyzes the rate-limiting step of amyloid-β protein (Aβ) generation, and is considered as a prime target for Alzheimer’s disease (AD). In search of a candidate for AD prevention, our efforts exploring the natural BACE1 inhibitor have led to the finding of nobiletin, tangeretin, and sinensetin—representative compounds of polymethoxyflavones (PMFs). Tangeretin exhibited the strongest BACE1 inhibition (IC50, 4.9 × 10−5 M), followed by nobiletin and sinensetin with IC50 values of 5.9 × 10−5 M and 6.3 × 10−5 M, respectively. In addition, all compounds reacted in a non-competitive manner with the substrate. Docking analysis results for complexes with BACE1 indicated that SER10 and THR232 residues of BACE1 hydrogen bonded with two oxygen atoms of tangeretin, while three additional BACE1 residues (ALA157, VAL336 and THR232) interacted with three oxygen atoms of nobiletin. Furthermore, sinensetin formed four hydrogen bonds through nitrogen atoms of TYR71, LYS75, and TRP76, and an oxygen atom of TYR198. Furthermore, the lowest-energy conformations of the most proposed complexes of sinensetin, nobiletin, and tangeretin with BACE1 were −7.2, −7.0, and −6.8 kcal/mol, respectively. Taken together, our results suggest that these polymethoxyflavones (PMFs) might be considered as promising BACE1 inhibitory agents that could lower Aβ production in AD.

Hepatoprotective and antineoplastic properties of Protaetia brevitarsis larvae

Protaetia brevitarsis larvae have been used as a traditional medicine to treat various liver diseases. Freeze‐dried powder and solvent partitioned fractions of Protaetia brevitarsis larvae, in this study, were examined for hepatoprotective and antitumor activities in vivo and in vitro. Oral administration of the powder reduced signs of acute and chronic liver injuries in diethylnitrosamine‐induced hepatotoxic mouse model. Various cancer cell types, but not normal primary hepatocytes, were killed by the hexane, ethyl acetate and butanol fractions, which were partitioned from larval extracts. Apoptosis and autophagy were primarily induced in cancer cells by hexane and ethyl acetate fractions, respectively, and can be the cytotoxic mechanisms of the fractions. Further analyses of the insect fractions could lead to identification of novel bioactive substances that can be exploited as therapeutics for various human liver diseases.