Prenylated Flavone from Roots of a Hybrid between Artocarpus heterophyllus and Artocarpus integer and its Biological Activities

Uma nova flavona prenilada, 2,8-dihodroxi-3,10-dimetoxi-6-(2-metil-1-propeno-1-il)6H,7H-[1]benzopirano[4,3-b][1]-benzopirano-7-ona, juntamente com 24 compostos conhecidos foram isolados do extrato bruto em acetona das raízes de um híbrido entre Artocarpus heterophyllus e Artocarpus integer. Suas estruturas foram determinadas pelos dados de espectroscopia da ressonância magnética nuclear (NMR) 1D e 2D. Avaliaram-se as atividades antioxidante e bactericida dos compostos isolados. O novo composto mostrou atividade antioxidante potente com relação a DPPH e superóxido com valores de IC50 de 0,033 e 0,125 mg mL , respectivamente.


Introduction
Artocarpus plants, belonging to the family Moraceae, are distributed in tropical and subtropical regions.Plants in this genus are rich in phenolic compounds, flavonoids, stilbenoids and arylbenzofurans. 1 Experimental studies performed in the past suggest that A. heterophyllus possesses diverse medicinal uses including antioxidant, anti-inflammatory, antibacterial, anticariogenic, antifungal, antineoplastic and hypoglycemic effects. 1,2orartocarpetin and artocarpesin isolated from the twigs and woods of A. heterophyllus showed good tyrosinase inhibitory activity. 3Artocarpanone from the roots of A. heterophyllus significantly inhibited the nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) in RAW 264.7 cell. 4Artocarpin isolated from the wood of A. heterophyllus showed potent cytotoxic activity on human T47D breast cancer cells. 5Prenylflavones, cycloheterophyllin and artonins A and B from A. heterophyllus showed lipid oxidation inhibitory activity, 6 whereas prenylated flavones from A. champeden (syn. A. integer Merr.) showed antimalarial activity. 7n Thailand, a hybrid between A. heterophyllus (jackfruit) and A. integer (champedak) has been developed for disease resistance, larger size of fruit with more firm aril texture and better taste than A. integer.There have been some reports on chemical studies on A. heterophyllus and A. integer, however, very little information is documented on A. heterophyllus root. 4In our preliminary study, the crude acetone extract from the roots of a hybrid between A. heterophyllus and A. integer exhibited antioxidant activity with IC 50 (IC 50 : sample concentration that produced 50% inhibition of the radical) values of 0.11 and 0.66 mg mL -1 in DPPH (1,1-diphenyl-2-picrylhydrazyl) and superoxide anion assays, respectively, and antibacterial activity against Acinetobacter baumannii and Escherichia coli with MIC Vol. 24, No. 10, 2013   (minimum inhibitory concentration) value lower than 3.125 µg mL -1 .Such results prompted us to investigate its chemical constituents in order to isolate bioactive constituents from this plant.

General procedures
Melting points were recorded on an Electrothermal 9100 melting point apparatus and are uncorrected.Infrared (IR) spectra were recorded using a FTS 165 FT-IR spectrometer (Perkin-Elmer 783).UV spectra were recorded on a SPECORD S 100 (Analytikjena), and optical rotations on a JASCO P-1020 polarimeter. 1 H and 13 C nuclear magnetic resonance (NMR) spectra were recorded on a Bruker FT-NMR Ultra Shield TM 300 MHz spectrometer using CDCl 3 solution unless otherwise stated with TMS (tetramethylsilane) as the internal standard.HRESIMS and LREIMS mass spectra were recorded on a Waters micromass and a Finnigan MAT 95 XL spectrometer, respectively.Vacuum liquid column chromatography (VLC) and column chromatography (CC) were carried out on 60H and 100 (70-230 mesh ASTM) silica gel (Merck) types, respectively, or on Sephadex LH-20 (GE Healthcare).Thin layer chromatograph (TLC) (thickness 200 mm) and precoated TLC (thickness 250 mm) were performed on F 254 silica gel 60 (Merck).

Plant material
The roots of a hybrid between A. heterophyllus and A. integer were collected from Nakhon Si Thammarat Province, in the Southern part of Thailand, in July 2009.The plant was identified by Prof. Kitichate Sridith and a voucher specimen (No. T. Kanogwan) has been deposited at the Herbarium of the Department of Biology, Faculty of Science, Prince of Songkla University, Songkhla, Thailand.

Free radical scavenging activity
In this study, DPPH, hydroxyl and superoxide radical scavenging assays were carried out, according to those previously described. 8tibacterial activity A modified broth microdilution method 9 was used to obtain the MIC values of the tested materials.20 µL of a 3-5 h culture of each bacterial strain (multidrugresistant Acinetobacter baumannii and Escherichia coli), containing approximately 5 × 10 4 CFU mL -1 , were applied into Muller-Hinton broth (MHB, Merck, Germany) supplemented with the plant extracts.100 µg of the extract and pure compounds were diluted in 1 mL of dimethyl sulfoxide (DMSO, Merck, Germany) and two-fold dilutions were made to obtain concentrations ranging from 0.05-100 µg mL -1 .The microtiter plates were incubated at 37 °C for 18 h.MICs were observed at least in duplicate as the lowest concentration of the plant extracts that produced a complete suppression of the bacterial growth.

Conclusions
This is the first report on the chemical constituents and biological activities from the roots of a hybrid between A. heterophyllus and A. integer.A new prenylated flavone (compound 1) was isolated from the roots of a hybrid between A. heterophyllus and A. integer together with 24 known compounds.Compound 1 demonstrated potent antioxidant activity against DPPH • and superoxide with IC 50 values of 0.033 and 0.125 mg mL -1 , respectively and strong  antibacterial activity against Acinetobacter baumannii with MIC value of 50 mg mL -1 .Among the known compounds, compounds 2, 3, 6, 7, 9, 16, 17, 23 and 25 are firstly reported from Artocarpus genus.