Human Neutrophil Elastase Inhibitory Dihydrobenzoxanthones And
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Ban et al. Appl Biol Chem (2020) 63:63 https://doi.org/10.1186/s13765-020-00549-3 ARTICLE Open Access Human neutrophil elastase inhibitory dihydrobenzoxanthones and alkylated favones from the Artocarpus elasticus root barks Yeong Jun Ban1†, Aizhamal Baiseitova1†, Mohd Azlan Nafah2, Jeong Yoon Kim1 and Ki Hun Park1* Abstract Neutrophil elastases are deposited in azurophilic granules interspace of neutrophils and tightly associated with infammatory ailments. The root barks of Artocarpus elasticus had a strong inhibitory potential against human neu- trophil elastase (HNE). The responsible components for HNE inhibition were confrmed as alkylated favones (2–4, IC50 14.8 ~ 18.1 μM) and dihydrobenzoxanthones (5–8, IC50 9.8 ~ 28.7 μM). Alkyl groups on favone were found to be crucial= functionalities for HNE inhibition. For instance, alkylated= favone 2 (IC 14.8 μM) was 20-fold potent than 50 = mother compound norartocarpetin (1, IC50 > 300 μM). The kinetic analysis showed that alkylated favones (2–4) were noncompetitive inhibition, while dihydrobenzoxanthones (5–8) were a mixed type I (KI < KIS) inhibitors, which usually binds with free enzyme better than to complex of enzyme–substrate. Inhibitors and HNE enzyme binding afnities were examined by fuorescence quenching efect. In the result, the binding afnity constants (KSV) had a signifcant correlation with inhibitory potencies (IC50). Keywords: Alkylated favones, Artocarpus elasticus, Dihydrobenzoxanthones, Fluorescence quenching, Human neutrophil elastase inhibition (HNE) Introduction defcient defence of the lower respiratory tract from Serine proteases are the largest and most important human neutrophil elastase (HNE), and further alveoli unit among the enzyme groups found in eukaryotes and damage [4]. Tis leads to the development of the chronic prokaryotes, which distinctively increases the reaction obstructive pulmonary disease, emphysema and lung of the peptide bonds hydrolysis [1]. One of them the cancer, also in the liver, it causes benign neonatal hepati- neutrophil elastase (NE, EC 3.4.21.37) 29 kDa chymot- tis syndrome, fbrosis which evolves to cirrhosis and even ripsis family protease, largely expressed by neutrophils to hepatocellular carcinoma [5]. Augmentation therapy precursors inside the bone marrow, then in its mature has been accepted as the best therapy for AAT defciency, active form they placed in primary (azurophilic) gran- and less costly methods such as low molecular weight NE ules [2]. Troughout infammation spread into the cell inhibitors have failed clinically, despite diligent eforts interspace NE activity closely contained by an abundant over the past three decades [6]. On the other hand, the blood plasma inhibitor—α1-antytrypsin (AAT) [3]. Te release of granular contents leads to the recruitment of stoppage of releasing AAT in hepatocytes expressively infammatory cells through cytokines (TNF-α, IL-1β, decreases its levels, leading to emphysema because of IL-6, IL-18, IL-10), adipokines (adiponectin, resistin and leptin), and chemokines (IL-8), which are the main intermediaries and progressors of renal tissue dam- *Correspondence: [email protected] †Yeong Jun Ban and Aizhamal Baiseitova contributed equally to this work age [7]. Tus, the invention of novel protease inhibitors 1 Division of Applied Life Science (BK21 plus), IALS, Gyeongsang National is an invaluable therapeutic tool. Tere have been many University, Jinju 52828, Republic of Korea attempts to develop lead structures for inhibiting HNE Full list of author information is available at the end of the article from plant sources [8, 9]. © The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creat iveco mmons .org/licen ses/by/4.0/. Ban et al. Appl Biol Chem (2020) 63:63 Page 2 of 8 Artocarpus elasticus, which common name is Terap, Extraction and isolation from the Moraceae family, distributed in the Asian trop- Extraction of A. elasticus barks (250 g) was done in meth- ics. Te plant is widely used in food: peeled shoot tips anol (10L), at approximately 25 °C, resulting to crude and feshy perianth can even be eaten raw, and the seeds reddish-brown colour gum (27 g). Te methanol extract are eaten fried. Te ripe fruits are edible, but they often was dried well and dissolved in 500 mL of water to be have an unpleasant smell. Leaves were used for nursing suspended for further fractionation into dark-red chloro- mothers, young leaves to treat vomiting, diseases related form extract (dry weight 14 g). Ten chloroform extract to blood, the bark inner side was used to treat sores, and was chromatographed by MCI GEL CHP20P (30 × 5 cm, latex also used in dysentery, fever, hypertension and dia- 75–150 μm, 500 g) column with step by step changing betes [10, 11]. Te therapeutic efect is associated with of water/methanol system (8:2 → 0:1) resulting to A1-15 the abundance of phenolics, such as favonoids, stilbe- fractions. Nonpolar A8-12 fractions (total 4.6 g) were noids, dihydrochalcones, dihydrobenzoxanthones and refractionated by MPLC (using ODS column 25 × 3 cm, prenylated favonoids [12]. Single metabolites reported S-10 μm, 12 nm, YMC) with a slow changing of solvents in vivo antimalarial [13], inhibition of LPS-induced from water to MeOH (0 → 100%) to give B1-80 subfrac- infammation [14], α-glucosidase inhibitory [15], TRAIL- tions. Te subfractions B26-35, totally 1.8 g, were fur- resistance overcoming with antiviral [16], and antican- ther subjected to recycling HPLC (using ODS column cer [17] activities. Alkylated favonoid Artonin E from 25 × 3 cm, S-5 μm, 12 nm, YMC), which resulted to A. elasticus also revealed considerable cytotoxic efect the isolation of compounds 1 (38 mg), 3 (21 mg), and 8 in MCF-7 human breast cancer cells by ROS mediated (35 mg). Likewise, the subfractions B36-43 total 1.4 g, mitochondrial pathway [18, 19]. In particular, metabo- were put to recycling HPLC to isolate dihydrobenzo- lites in A. elasticus has not been reported to have HNE xanthone 5 (14 mg), 6 (22 mg), and alkylated favone 4 inhibitory potential capacity. (19 mg). In the same way, the subfractions B44-56 (1.5 g) Te aim of the present study was the investigation of were also recycled on HPLC to purify compounds 2 HNE inhibitory potential of the root barks of A. elasti- (12 mg) and 7 (18 mg). Purifcation of compounds done cus, and to isolate the responsible components for HNE on Sephadex-LH20. inhibition. Te inhibitory mechanisms were fully char- acterized by double reciprocal plots from the Michaelis– Measurement of HNE inhibitory activity Menten equation. We also tried to determine the binding Te inhibitory activity of HNE (EC 3.4.21.37) was ana- afnities of the isolated inhibitors to HNE enzyme by lysed by measuring of the hydrolysis of N-methoxysucci- fuorescence (FS) quenching experiment. nyl-Ala–Ala-Pro-Cal-p-nitroanilide at 405 nm in optimal pH of 8.0 (0.02 mM, Tris–HCl bufer) and at 37 °C [8]. In brief, to 96-well plates 10 μL the inhibitors or cafeic Materials and methods acid as a control (dissolved in DMSO), 40 μL substrate Instruments and chemicals (MeOSuc-AAPV-pNA, 1.5 mM), 130 μL of bufer and 20 Bruker AM500 spectrometer (Karlsruhe, Germany) used μL enzyme (stock concentration 0.2 unit/mL) mixed. Te for measurement of proton and carbon-13 NMR spec- concentration of 50% inhibition of the enzyme (IC 50) was tra. By mass spectrometer JEOL JMS-700 (Tokyo, Japan) expressed as compounds activity. Inhibition rate (%) cal- obtained all mass data. Forte/R 100 (YMC, Kyoto, Japan) culated by next Eq. (1): recycling HPLC and MPLC with Triart C18 column (YMC, Japan) used for isolation of compounds. Metha- Activity (%) = [1 + ([I]/IC50)]×100 (1) nol, acetonitrile, water and acetic acid of the analytical grade for HPLC were purchased from Fisher Scientifc HNE inhibitory kinetic assay (Korea). For performing enzyme assays SpectraMax M3 Multi-Mode Microplate Reader (Molecular device, USA) By the same way with activity experiments, the enzyme was used. HNE (EC 3.4.21.37) was ordered from Sigma kinetic behaviours were identifed using MeOSuc-AAPV- Aldrich (St. Louis, USA). pNA substrate concentrations of 0, 0.75, 1.5, and 3 mM with diferent concentrations of inhibitors [8]. Data analysis on Sigma Plot (Chicago, USA) used to deter- Plant material mine the variables of curves. By Lineweaver–Burk plots, Collection in December 2013 and storage until extraction kinetic values such as Michaelis–Menten (Km) and maxi- of Malaysian the A. elasticus barks done by associated mum velocity (Vmax) were determined. From Dixon plots, professor Dr. Mohd Azlan Nafah. Te voucher of the enzyme and inhibitors (Ki) dissociation constants calcu- specimen (TM1016) was given in the Universiti Pendidi- lated. Constants of inhibitions when compounds binding kan Sultan Idris, Malaysia. whether free enzyme or else enzyme–substrate complex, Ban et al. Appl Biol Chem (2020) 63:63 Page 3 of 8 were calculated from plots of the slopes of the straight degrees from calculation of double bonds. Te D-ring lines (KI) or vertical intercept (KIS) verse the concentra- was deduced by the unique of endomethylene H9a/b (δH tion of inhibitors by Eqs.