Niebla homalea Rundel & Bowler
Creators: name: Zhang, Yan
name: Tan, Choon Yong
name: Spjut, Richard W.
name: Fuchs, James R.
name: Kinghorn, A. Douglas
name: Rakotondraibe, Liva Harinantenaina
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Fungi
Ascomycota
Lecanoromycetes
Lecanorales
Ramalinaceae
Niebla
Niebla homalea

description: 3.3. Extraction and isolation of secondary metabolites of Niebla homalea   
 The lichen Niebla homalea (Ach.) Rundel & Bowler (62 g) was macerated for 1 week with 3 L of ethyl acetate. The extract was filtered and concentrated in vacuo to yield 4 g of a brown residue. This ethyl acetate residue was subjected to passage over a silica gel column [SiliaFlash® P60 (230–400 mesh)], and eluted sequentially with hexane containing increasing amounts of ethyl acetate (1:0, 20:1, 10:1, 5:1, 2:1, 1:1, and 0:1), to afford ten major fractions labeled N1 to N10. Fraction N2 (20 mg) yielded compound 6 (5 mg) by precipitation in chloroform (CHCl 3). Fractions N3 (6 mg) and N4 were washed with chloroform to afford compounds 4 (1 mg) and 7 (6 mg), respectively. Fraction N5 (40 mg) was purified using a C 18 column (CH 3 CN–H 2 O, 7:3) to give 5 (3 mg). Fraction N6 (40 mg) was purified also via a C 18 column (CH 3 CN–H 2 O, 3:2) to yield compound 9 (3 mg). Fraction N7 (120 mg) was chromatographed over a Sephadex LH-20 column with hexane-CHCl 3 -MeOH (5:5:1) as solvent and washed with hexanes-CHCl 3 -MeOH (5:5:1) to afford 11 (6 mg). Fraction N8 (170 mg) was chromatographed over a Sephadex LH-20 column, eluted with hexanes-CHCl 3 -MeOH (5:5:1), and further purified via silica gel column chromatography (hexanes-EtOAc, 5:1) to yield 12 (4 mg) and 8 (4 mg). Fraction N9 (130 mg) was chromatographed over a Sephadex LH-20 column with hexanes-CHCl 3 - MeOH (5:5:1) and further purified via a C 18 column (CH 3 CN–H 2 O, 7:3) to yield compounds 2 (2 mg) and 3 (2 mg). Fraction N10 (70 mg) was chromatographed over a Sephadex LH-20 column with hexanes-CHCl 3 - MeOH (5:5:1) and washed with hexanes-CHCl 3 -MeOH (5:5:1) to yield 3 mg of 1 and 4 mg of 10.   
 Anaya-Eugenio, G.D., Tan, C.Y., Rakotondraibe, L.H., Carcache de Blanco, E.J., 2020. Tumor suppressor p53 independent apoptosis in HT-29 cells by auransterol from Penicillium aurantiacobrunneum. Biomed. Pharmacother. 127, 110124. https://doi. org/10.1016/j.biopha.2020.110124.   
*Assignments based on HSQC and HMBC spectra.  
 Carpentier, C., Queiroz, E.F., Marcourt, L., Wolfender, J.-L., Azelmat, J., Grenier, D., Boudreau, S., Voyer, N., 2017. Dibenzofurans and pseudodepsidones from the lichen Stereocaulon paschale collected in northern Quebec. J. Nat. Prod. 80, 210–214.   
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Connolly, J.D., 1977. Triterpenoids. In: Terpenoids and Steroids, Vol. 7. Royal Society of Chemistry, Cambridge, UK, pp. 130–154.  
 Nieblastictane A (8S,9S,10R,14S,17R,18S,21R, 22R)-22α- hydroxystictan-3-on-30-oic acid, 1): white amorphous powder; [α] 20 D +66.0 (c 0.001, MeOH); IR (KBr) ν max: 3465, 2956, 2875, 1699, 1471, 1385, 1241, 754, 667 cm 1; 1 H NMR (400 MHz, CDCl 3) and 13 C NMR (100 MHz, CDCl 3) data, see Table 1; HRESIMS m / z 495.3447 [M + Na] + (calcd. for C 30 H 48 O 4 Na +: 495.3445).   
 Connolly, J.D., Freer, A.A., Kalb, K., Huneck, S., 1984. Lichen substances. Part 141. Eriodermin, a dichlorodepsidone from the lichen Erioderma physcioides - crystal structure analysis. Phytochemistry 23, 857–858.   
Corbett, R.E., Wilkins, A.L., 1976a. Lichens and fungi. Part XII. Dehydration and isomerization of stictane triterpenoids. J. Chem. Soc., Perkin Trans. 1, 857–863.  
Corbett, R.E., Wilkins, A.L., 1976b. Lichens and fungi. Part XIII. Comparison of the nuclear magnetic resonance and mass spectra of 17,21-secohopane and 17,21- secoflavicane derivatives. J. Chem. Soc., Perkin Trans. 1, 1316–1320.  
 Nieblastictane B (8S,9S,10R,14S,17R,18S,21S,22R)-22α- Hydroxysticta-3-on-29 oic acid, 2): white amorphous powder; [α] 20 D +24.0 (c 0.001, MeOH); IR (KBr) ν max 3390, 2956, 2873, 1702, 1457, 1385, 1230, 1057, 755 cm 1; 1 H NMR (400 MHz, CDCl 3) and 13 C NMR (100 MHz, CDCl 3) data, see Table 1; HRESIMS m / z 495.3440 [M +Na] + (calcd. for C 30 H 48 O 4 Na +: 495.3445).   
Corbett, R.E., Heng, C.K., Wilkins, A.L., 1976. Lichens and fungi. XIV. A revised structure for retigerane triterpenoids. Aust. J. Chem. 29, 2567–2570.  
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 Nieblastictane C (2R,8S,9S,10R,12S,13S,14S,17R,18S,21R,22R)-2- chloro-12, 22-dihydroxystictan-3-one (3): white amorphous powder; [α] 20 D 1.00 (c 0.001, MeOH); IR (KBr) ν max 3411, 2945, 2873, 1709, 1458, 1386, 1217, 1059, 1022, 755 cm 1; 1 H NMR (400 MHz, CDCl 3) and 13 C NMR (100 MHz, CDCl 3) data, see Table 1; HRESIMS m / z 515.3268 [M + Na] + (calcd. for C 30 H 49 O 3 ClNa, 515.3262).   
 Elix, J.A., Whitton, A.A., Jones, A.J., 1982. Triterpenes from the lichen genus Physcia. Aust. J. Chem. 35, 641–647.   
Gollapudi, S.R., Telikepalli, H., Jampani, H.B., Mirhom, Y.W., Drake, S.D.,  
 Bhattiprolu, K.R., Vander Velde, D., Mitscher, L.A., 1994. Alectosarmentin, a new antimicrobial dibenzofuranoid lactol from the lichen, Alectoria sarmentosa. J. Nat. Prod. 57, 934–938.   
 Gonzalez, A.G., Barrera, J.B., Rodriguez Perez, E.M., 1991. Chemical constituents of the lichen Cladina macaronesica. Z. Naturforsch., C: Biosci. 46, 12–18.   
 Nieblaflavicane A (8S,9S,10R,14S,17R,18S,21S)-30-nor-21βH-flavican-3,22-dione, 4): thin white needles (CH 2 Cl 2 – CH 3 OH); [α] 20 D 127.2 (c 0.001, MeOH); IR (KBr) ν max 2928, 1704, 1383 cm 1; 1 H NMR (400 MHz, CDCl 3) and 13 C NMR (100 MHz, CDCl 3) data, see Table 2; HRESIMS m / z 449.3394 [M +Na] + (calcd. for 449.3396, C 29 H 46 O 2 Na).   
 Nieblaflavicane B (8S,9S,10R,14S,17R,18S) -22,29,30- trinor-flavican-3,21-dione, 5): white needles (CH 2 Cl 2 – CH 3 OH); [α] 20 D +3.0 (c 0.001, MeOH); IR (KBr) ν max 2928, 2869, 1734, 1705, 1461, 1384, 1110 cm 1; 1 H NMR (400 MHz, CDCl 3) and 13 C NMR (100 MHz, CDCl 3) data, see Table 2; HRESIMS m / z 421.3088 [M + Na] + (calcd. for 421.3083, C 27 H 42 O 2 Na).    3.4. Cytotoxicity assay   
The cytotoxic activities of the isolates were evaluated against human hormone-dependent breast (MCF-7) and ovarian (A2780) cancer cell lines, according to a previously described protocol and paclitaxel and camptothecin were used as positive controls (Tan et al., 2019).  
 Funding   
This project was supported by supplement 3P01CA125066-09/10S1 of a NIH / NCI program grant (P01CA125066). We thank the College of Pharmacy and the Campus Chemical Instrument Center (CCIC) instrumentation facilities for access to NMR and MS equipment.  Declaration of competing interest  
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.  Appendix A. Supplementary data  
Supplementary data to this article can be found online at https://doi. org/10.1016/j.phytochem.2020.112521.  References  
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description: Published as part of Zhang, Yan, Tan, Choon Yong, Spjut, Richard W., Fuchs, James R., Kinghorn, A. Douglas & Rakotondraibe, Liva Harinantenaina, 2020, Specialized metabolites of the United States lichen Niebla homalea and their antiproliferative activities, pp. 1-7 in Phytochemistry (112521) (112521) 180 on pages 5-7, DOI: 10.1016/j.phytochem.2020.112521, http://zenodo.org/record/8301840