[en] In this work, the optimization of phenolic compounds extraction from Eucalyptus camaldulensis leaves was carried out by applying a response surface methodology (RSM) approach. The influence of different parameters i.e., the liquid-to-solid ratio, the temperature and the extraction time have been jointly tested by maceration in an ethanol–water (70/30; v/v) mixture. A central composite design composed of 20 experimental trials with 6 replicates in the center was applied. A second-order polynomial model was used to describe the experimental data related to the extraction yield, the Total Phenolic Content (TPC), the total content of the major flavonoid compounds identified and quantified by high performance liquid chromatography–electrospray ionization mass spectrometry (HPLC–ESI–MS), and antioxidant activity by DPPH (2,2-diphenyl-l-picrylhydrazyl) and FRAP (ferric reducing antioxidant power) assays. The optimum extraction conditions obtained were 12.4 mL/g, 50.4 °C, and 124.8 min, for liquid/solid ratio, temperature and contact time, respectively. Under these conditions, the predicted phenolic compound content was 342.8 ± 11.1 mg GAE/g dry extract. Analysis of variance (ANOVA) showed a good fit (p < 0.05) between the predicted and observed responses for each response variable studied. The extracts showed a significative correlation (80%) between the TPC and their antioxidant activities using DPPH assays. HPLC–ESI–MS and tandem mass spectrometry (MSn) analysis of the extracts allowed to identify eight major glycosylate flavonoids. E. camaldulensis leaf extracts present a wide range of phenolic compounds with interest in market garden crops.
Ouattara, Bassalia; Laboratoire Energies Renouvelables et Efficacité Energétique (LabEREE), Institut International d’Ingénierie de l’Eau et de l’Environnement (2iE), Ouagadougou 01, Burkina Faso ; Organic Synthesis and Mass Spectrometry Lab, Biosciences Research Institute, University of MONS–UMONS, Mons, Belgium
Semay, Irène ; Université de Mons - UMONS > Faculté des Science > Service de Synthèse et spectrométrie de masse organiques
Ouedraogo, Jean-Claude ; Université de Mons - UMONS > Faculté des Sciences > Service de Synthèse et spectrométrie de masse organiques ; Laboratoire de Chimie Analytique Environnementale et Bio-Organique (LCAEBiO), Université Joseph KI-ZERBO, Ouagadougou 03, Burkina Faso
Gerbaux, Pascal ; Université de Mons - UMONS > Faculté des Science > Service de Synthèse et spectrométrie de masse organiques
Ouédraogo, Igor W. K. ; Laboratoire Energies Renouvelables et Efficacité Energétique (LabEREE), Institut International d’Ingénierie de l’Eau et de l’Environnement (2iE), Ouagadougou 01, Burkina Faso
Language :
English
Title :
Optimization of the Extraction of Phenolic Compounds from Eucalyptus camaldulensis Dehnh Leaves Using Response Surface Methodology
Publication date :
22 November 2023
Journal title :
Chemistry Africa
ISSN :
2522-5758
eISSN :
2522-5766
Publisher :
Springer Science and Business Media Deutschland GmbH
S836 - Synthèse et spectrométrie de masse organiques
Research institute :
R100 - Institut des Biosciences
Funders :
Académie de recherche et d'enseignement supérieur
Funding text :
This research was supported by the Académie de Recherche et de l’Enseignement Supérieur- Commission de la Coopération au Développement (ARES-CCD) de la Fédération Wallonie Bruxelles (Belgium).
Stanaway JD, Afshin A, Ashbaugh C, Bisignano C, Brauer M, Ferrara G, Garcia V, Haile D, Hay SI, He J (2022) Health effects associated with vegetable consumption: a Burden of Proof study. Nat Med. 10.1038/s41591-022-01970-5- DOI: 10.1038/s41591-022-01970-5-
Son D, Somda I, Legreve A, Schiffers B (2017) Pratiques phytosanitaires des producteurs de tomates du Burkina Faso et risques pour la santé et l’environnement. Cah Agric. 10.1051/cagri/2017010 DOI: 10.1051/cagri/2017010
Tarnagda B, Tankoano A, Tapsoba F, Pane BS, Hissein OA, Djbrine AO, Drabo KM, Traoré Y, Savadogo A (2017) Évaluation des pratiques agricoles des légumes feuilles: le cas des utilisations des pesticides et des intrants chimiques sur les sites maraîchers de Ouagadougou, Burkina Faso. J Appl Biosci. 10.4314/jab.v117i1.3 DOI: 10.4314/jab.v117i1.3
Lehmann E, Oltramare C, Dibié JJN, Konaté Y, De Alencastro LF (2018) Assessment of human exposure to pesticides by hair analysis: the case of vegetable-producing areas in Burkina Faso. Environ Int. 10.1016/j.envint.2017.10.025 DOI: 10.1016/j.envint.2017.10.025
Ouédraogo RA, Kambiré FC, Kestemont MP, Bielders CL (2019) Caractériser la diversité des exploitations maraîchères de la région de Bobo-Dioulasso au Burkina Faso pour faciliter leur transition agroécologique. Cah Agric. 10.1051/cagri/2019021 DOI: 10.1051/cagri/2019021
Lehmann E, Turrero N, Kolia M, Konaté Y, De Alencastro LF (2017) Dietary risk assessment of pesticides from vegetables and drinking water in gardening areas in Burkina Faso. Sci Total Environ. 10.1016/j.scitotenv.2017.05.285 DOI: 10.1016/j.scitotenv.2017.05.285
Son D, Zerbo FKB, Bonzi S, Schiffers B, Somda I, Schiffers B, Legreve A (2018) Assessment of tomato (Solanum lycopersicum L.) producers’ exposure level to pesticides, in Kouka and Toussiana (Burkina Faso). Int J Environ Res Public Health. 10.3390/ijerph15020204 DOI: 10.3390/ijerph15020204
Tir M, Mufti A, Feriani A, Saadaoui E, El Cafsi M, Tlili N (2023) Eucalyptus camaldulensis seeds as a potential source of beneficial compounds: high-performance liquid chromatography-photodiode array–mass spectrometry (HPLC-PDA-MS/MS) profiling of secondary metabolites and the assessment of the biological effects. Anal Lett. 10.1080/00032719.2022.2139383 DOI: 10.1080/00032719.2022.2139383
Aleksic SV, Knezevic P (2019) Antimicrobial activity of Eucalyptus camaldulensis Dehn. plant extracts and essential oils: a review. Ind Crops Prod. 10.1016/j.indcrop.2019.02.051 DOI: 10.1016/j.indcrop.2019.02.051
Gomes F, Martins N, Barros L, Rodrigues ME, Oliveira MBPP, Henriques M, Ferreira ICFR (2018) Plant phenolic extracts as an effective strategy to control Staphylococcus aureus, the dairy industry pathogen. Ind Crops Prod. 10.1016/j.indcrop.2017.12.027 DOI: 10.1016/j.indcrop.2017.12.027
Sah SY, Sia CM, Chang SK, Ang YK, Yim HS (2012) Antioxidant capacity and total phenolic content of lemon grass (Cymbopogon citratus) leave. Ann Food Sci Technol 13:150–155
Park JY, Son YG, Kang SD, Lee SW, Kim KD, Kim JY (2023) Characterization of chemical composition and antioxidant activity of Eucalyptus globulus leaves under different extraction conditions. Appl Sci. 10.3390/app13179984 DOI: 10.3390/app13179984
Batish DR, Singh HP, Kohli RK, Kaur S (2008) Eucalyptus essential oil as a natural pesticide. For Ecol Manag. 10.1016/j.foreco.2008.08.008 DOI: 10.1016/j.foreco.2008.08.008
Baeshen RS, Baz MM (2023) Efficacy of Acacia nilotica, Eucalyptus camaldulensis, and Salix safsafs on the mortality and development of two vector-borne mosquito species, Culex pipiens and Aedes aegypti, in the laboratory and field. Heliyon. http://creativecommons.org/licenses/by/4.0/
Ghareeb MA, Habib MR, Mossalem HS, Abdel-Aziz MS (2018) Phytochemical analysis of Eucalyptus camaldulensis leaves extracts and testing its antimicrobial and schistosomicidal activities. Bull Natl Res Cent. 10.1186/s42269-018-0017-2 DOI: 10.1186/s42269-018-0017-2
Ashraf A, Sarfraz RA, Mahmood A, Din M (2015) Chemical composition and in vitro antioxidant and antitumor activities of Eucalyptus camaldulensis Dehn. leaves. Ind Crops Prod. 10.1016/j.indcrop.2015.04.059 DOI: 10.1016/j.indcrop.2015.04.059
Dkhil MA, Aljawdah HMA, Abdel-gaber R, Thagfan FA, Delic D, Al-quraishy S (2023) The effect of Eucalyptus camaldulensis leaf extracts from different environmental harvesting locations on Plasmodium chabaudi-induced malaria outcome. Food Sci Technol. 10.1590/fst.006723 DOI: 10.1590/fst.006723
Nasr A, Saleem KT, Zhu GP (2019) Phenolic compounds and antioxidants from Eucalyptus camaldulensis as affected by some extraction conditions, a preparative optimization for GC-MS analysis. Prep Biochem Biotechnol. 10.1080/10826068.2019.1575860 DOI: 10.1080/10826068.2019.1575860
Alghoraibi I, Soukkarieh CH, Zein R, Alahmad A, Walter JG, Daghestani M (2020) Aqueous extract of Eucalyptus camaldulensis leaves as reducing and capping agent in biosynthesis of silver nanoparticles. Inorg Nano-Met Chem. 10.1080/24701556.2020.1728315 DOI: 10.1080/24701556.2020.1728315
Rosendal E, Ouédraogo JCW, Dicko C, Dey ES, Bonzi-Coulibaly YL (2020) Geographical variation in total phenolics, flavonoids and antioxidant activities of Eucalyptus camaldulensis leaves in Burkina Faso. Afr J Pure Appl Chem. 10.5897/AJPAC2020.0837 DOI: 10.5897/AJPAC2020.0837
Wong-Paz JE, Contreras-Esquivel JC, Rodríguez-Herrera R, Carrillo-Inungaray ML, López LI, Nevárez-Moorillón GV, Aguilar CN (2015) Total phenolic content, in vitro antioxidant activity and chemical composition of plant extracts from semiarid Mexican region. Asian Pac J Trop Med. 10.1016/S1995-7645(14)60299-6 DOI: 10.1016/S1995-7645(14)60299-6
Majeed M, Hussain AI, Chatha SAS, Khosa MKK, Kamal GM, Kamal MA, Zhang X, Liu M (2016) Optimization protocol for the extraction of antioxidant components from Origanum vulgare leaves using response surface methodology. Saudi J Biol Sci. 10.1016/j.sjbs.2015.04.010 DOI: 10.1016/j.sjbs.2015.04.010
Mahmoudian F, Moghaddam AH, Davachi SM (2022) Genetic-based multi-objective optimization of alkylation process by a hybrid model of statistical and artificial intelligence approaches. Can J Chem Eng. 10.1002/cjce.24072 DOI: 10.1002/cjce.24072
Moghaddam AH (2022) Simulation and optimization of separation section in methanol to olefin (MTO) process based on statistical approach. Chem Pap. 10.1007/s11696-022-02190-4 DOI: 10.1007/s11696-022-02190-4
Moghaddam AH (2023) Investigation and optimization of olefin purification in methanol-to-olefin process based on machine learning approach coupled with genetic algorithm. Korean J Chem Eng. 10.1007/s11814-023-1384-4 DOI: 10.1007/s11814-023-1384-4
Thiex N, Novotny L, Crawford A (2012) Determination of ash in animal feed: AOAC official method 942.05 revisited. J AOAC Int. 10.5740/jaoacint.12-129 DOI: 10.5740/jaoacint.12-129
Vaziri H, Moghaddam AH, Mirmohammadi SA (2020) Optimization of distillation column in phenol production process for increasing the isopropyl benzene concentration using response surface methodology and radial basis function (RBF) coupled with leave-one-out validation method. Chem Pap. 10.1007/s11696-020-01162-w DOI: 10.1007/s11696-020-01162-w
Gulcin I (2020) Antioxidants and antioxidant methods: an updated overview. Arch Toxicol. 10.1007/s00204-020-02689-3 DOI: 10.1007/s00204-020-02689-3
Woisky RG, Salatino A (1998) Analysis of propolis: some parameters and procedures for chemical quality control. J Apic Res. 10.1080/00218839.1998.11100961 DOI: 10.1080/00218839.1998.11100961
Parejo I, Viladomat F, Bastida J, Rosas-Romero A, Saavedra G, Murcia MA, Jiménez AM, Codina C (2003) Investigation of Bolivian plant extracts for their radical scavenging activity and antioxidant activity. Life Sci. 10.1016/S0024-3205(03)00488-0 DOI: 10.1016/S0024-3205(03)00488-0
Benzie IFF, Strain JJ (1996) The ferric reducing ability of plasma (FRAP) as a measure of “antioxidant power: the FRAP assay. Anal Biochem. 10.1006/abio.1996.0292 DOI: 10.1006/abio.1996.0292
Maran JP, Manikandan S, Priya B, Gurumoorthi P (2015) Box-Behnken design based multi-response analysis and optimization of supercritical carbon dioxide extraction of bioactive flavonoid compounds from tea (Camellia sinensis L.) leaves. J Food Sci Technol. 10.1007/s13197-013-0985-z DOI: 10.1007/s13197-013-0985-z
Zieliński H, Kozłowska H (2000) Antioxidant activity and total phenolics in selected cereal grains and their different morphological fractions. J Agric Food Chem. 10.1021/jf990619o DOI: 10.1021/jf990619o
Drosou C, Kyriakopoulou K, Bimpilas A, Tsimogiannis D, Krokida M (2015) A comparative study on different extraction techniques to recover red grape pomace polyphenols from vinification byproducts. Ind Crops Prod. 10.1016/j.indcrop.2015.05.063 DOI: 10.1016/j.indcrop.2015.05.063
Ozay Y, Ozdemir S, Gonca S, Canli O, Dizge N (2021) Phenolic compounds recovery from pistachio hull using pressure-driven membrane process and a cleaner production of biopesticide. Environ Technol Innov. 10.1016/j.eti.2021.101993 DOI: 10.1016/j.eti.2021.101993
Wong-Paz JE, Muñiz MDB, Martínez ÁGCG, Belmares CRE, Aguilar CN (2015) Ultrasound-assisted extraction of polyphenols from native plants in the Mexican desert. Ultrason Sonochem. 10.1016/j.ultsonch.2014.06.001 DOI: 10.1016/j.ultsonch.2014.06.001
Costa P, Gonçalves S, Valentão P, Andrade PB, Coelho N, Romano A (2012) Thymus lotocephalus wild plants and in vitro cultures produce different profiles of phenolic compounds with antioxidant activity. Food Chem. 10.1016/j.foodchem.2012.05.072 DOI: 10.1016/j.foodchem.2012.05.072
Mylonaki S, Kiassos E, Makris DP, Kefalas P (2008) Optimisation of the extraction of olive (Olea europaea) leaf phenolics using water/ethanol-based solvent systems and response surface methodology. Anal Bioanal Chem. 10.1007/s00216-008-2353-9 DOI: 10.1007/s00216-008-2353-9
Sultana B, Anwar F, Ashraf M (2009) Effect of extraction solvent/technique on the antioxidant activity of selected medicinal plant extracts. Molecules. 10.3390/molecules14062167 DOI: 10.3390/molecules14062167
Trabelsi N, Megdiche W, Ksouri R, Falleh H, Oueslati S, Soumaya B, Hajlaoui H, Abdelly C (2010) Solvent effects on phenolic contents and biological activities of the halophyte Limoniastrum monopetalum leaves. LWT-Food Sci Technol. 10.1016/j.lwt.2009.11.003 DOI: 10.1016/j.lwt.2009.11.003
Gullón B, Muñiz-Mouro A, Lú-Chau TA, Moreira MT, Lema JM, Eibes G (2019) Green approaches for the extraction of antioxidants from eucalyptus leaves. Ind Crops Prod. 10.1016/j.indcrop.2019.111473 DOI: 10.1016/j.indcrop.2019.111473
Liu Y, Wei S, Liao M (2013) Optimization of ultrasonic extraction of phenolic compounds from Euryale ferox seed shells using response surface methodology. Ind Crops Prod. 10.1016/j.indcrop.2013.07.023 DOI: 10.1016/j.indcrop.2013.07.023
Skrypnik L, Novikova A (2020) Response surface modeling and optimization of polyphenols extraction from apple Pomace based on nonionic emulsifiers. Agronomy. 10.3390/agronomy10010092 DOI: 10.3390/agronomy10010092
Palma A, Díaz MJ, Ruiz-Montoya M, Morales E, Giráldez I (2021) Ultrasound extraction optimization for bioactive molecules from Eucalyptus globulus leaves through antioxidant activity. Ultrason Sonochem. 10.1016/j.ultsonch.2021.105654 DOI: 10.1016/j.ultsonch.2021.105654
Bhuyan DJ, Vuong QV, Chalmers AC, Altena IAV, Bowyer MC, Scarlett C (2015) Investigation of phytochemicals and antioxidant capacity of selected Eucalyptus species using conventional extraction. Chem Pap. 10.1515/chempap-2015-0237 DOI: 10.1515/chempap-2015-0237
Clarke G, Ting K, Wiart C, Fry J (2013) High correlation of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, ferric reducing activity potential and total phenolics content indicates redundancy in use of all three assays to screen for antioxidant activity of extracts of plants from the Malaysian rainforest. Antioxidants. 10.3390/antiox2010001 DOI: 10.3390/antiox2010001
Marslin G, Siram K, Maqbool Q, Selvakesavan R, Kruszka D, Kachlicki P, Franklin G (2018) Secondary metabolites in the green synthesis of metallic nanoparticles. Materials. 10.3390/ma11060940 DOI: 10.3390/ma11060940
Wang Y, Gao Y, Ding H, Liu S, Han X, Gui J, Liu D (2017) Subcritical ethanol extraction of flavonoids from Moringa oleifera leaf and evaluation of antioxidant activity. Food Chem. 10.1016/j.foodchem.2016.09.058 DOI: 10.1016/j.foodchem.2016.09.058
Gullón B, Gullón P, Lú-Chau TA, Moreira MT, Lema JM, Eibes G (2017) Optimization of solvent extraction of antioxidants from Eucalyptus globulus leaves by response surface methodology: Characterization and assessment of their bioactive properties. Ind Crops Prod. 10.1016/j.indcrop.2017.07.014 DOI: 10.1016/j.indcrop.2017.07.014
Cordeiro AMTM, Medeiros ML, Santos NA, Soledade LEB, Pontes LFBL, Souza AL, Queiroz N, Souza A (2013) Rosemary (Rosmarinus officinalis L.) extract. J Therm Anal Calorim. 10.1007/s10973-012-2778-4 DOI: 10.1007/s10973-012-2778-4
Liyanapathirana C, Shahidi F (2005) Optimization of extraction of phenolic compounds from wheat using response surface methodology. Food Chem. 10.1016/j.foodchem.2004.08.050 DOI: 10.1016/j.foodchem.2004.08.050
Chaaban H, Ioannou I, Chebil L, Slimane M, Gérardin C, Paris C, Charbonnel C, Chekir L, Ghoul M (2017) Effect of heat processing on thermal stability and antioxidant activity of six flavonoids. J Food Process Preserv. 10.1111/jfpp.13203 DOI: 10.1111/jfpp.13203
Francisco JC, Sivik B (2002) Solubility of three monoterpenes, their mixtures and eucalyptus leaf oils in dense carbon dioxide. J Supercrit Fluids. 10.1016/S0896-8446(01)00131-0 DOI: 10.1016/S0896-8446(01)00131-0
Lu Q, Peng Y, Zhu C, Pan S (2018) Effect of thermal treatment on carotenoids, flavonoids and ascorbic acid in juice of orange. Food Chem. 10.1016/j.foodchem.2018.05.072 DOI: 10.1016/j.foodchem.2018.05.072
Cao H, Saroglu O, Karadag A, Diaconeasa Z, Zoccatelli G, Conte-Junior CA, Gonzalez-Aguilar GA, Ou J, Bai W, Zamarioli CM, de Freitas LAP, Shpigelman A, Campelo PH, Capanoglu E, Hii CL, Jafari SM, Qi Y, Liao P, Wang M, Zou L, Bourke P, Simal-Gandara J, Xiao J (2021) Available technologies on improving the stability of polyphenols in food processing. Food Front. 10.1002/fft2.65 DOI: 10.1002/fft2.65
Amakura Y, Umino Y, Tsuji S, Ito H, Hatano T, Yoshida T, Tonogai Y (2002) Constituents and their antioxidative effects in eucalyptus leaf extract used as a natural food additive. Food Chem. 10.1016/S0308-8146(01)00321-1 DOI: 10.1016/S0308-8146(01)00321-1
Nwabor OF, Singh S, Syukri DM, Voravuthikunchai SP (2021) Bioactive fractions of Eucalyptus camaldulensis inhibit important foodborne pathogens, reduce listeriolysin O-induced haemolysis, and ameliorate hydrogen peroxide-induced oxidative stress on human embryonic colon cells. Food Chem. 10.1016/j.foodchem.2020.128571 DOI: 10.1016/j.foodchem.2020.128571
Meksem N, Bordjiba O, Nedjoud G, Farfar M, Amara LM, Djebar MR (2016) Study of the antimicrobial activity of the extracts of the Eucalyptus camaldulensis and Eucalyptus globulus stemming from the Algerian Northeast. Int J Pharm Sci Rev Res 39:1–5
Santos MCP, Gonçalves ÉCBA (2016) Effect of different extracting solvents on antioxidant activity and phenolic compounds of a fruit and vegetable residue flour. Sci Agropecu. 10.17268/sci.agropecu.2016.01.01 DOI: 10.17268/sci.agropecu.2016.01.01
Santos SAO, Villaverde JJ, Freire CSR, Domingues MRM, Neto CP, Silvestre AJD (2012) Phenolic composition and antioxidant activity of Eucalyptus grandis, E. urograndis (E. grandis × E. urophylla) and E. maidenii bark extracts. Ind Crops Prod. 10.1016/j.indcrop.2012.02.003 DOI: 10.1016/j.indcrop.2012.02.003
Kachlicki P, Piasecka A, Stobiecki M, Marczak L (2016) Structural characterization of flavonoid glycoconjugates and their derivatives with mass spectrometric techniques. Molecules. 10.3390/molecules21111494 DOI: 10.3390/molecules21111494
Chen Y, Yu H, Wu H, Pan Y, Wang K, Jin Y, Zhang C (2015) Characterization and quantification by LC-MS/MS of the chemical components of the heating products of the flavonoids extract in pollen Typhae for transformation rule exploration. Molecules. 10.3390/molecules201018352 DOI: 10.3390/molecules201018352
Cuyckens F, Claeys M (2004) Mass spectrometry in the structural analysis of flavonoids. J Mass Spectrom. 10.1002/jms.585- DOI: 10.1002/jms.585-
Figueirinha A, Paranhos A, Pérez-Alonso JJ, Santos-Buelga C, Batista MT (2008) Cymbopogon citratus leaves: characterization of flavonoids by HPLC–PDA–ESI/MS/MS and an approach to their potential as a source of bioactive polyphenols. Food Chem. 10.1016/j.foodchem.2008.02.045 DOI: 10.1016/j.foodchem.2008.02.045
Hassan WHB, Abdelaziz S, Al Yousef HM (2019) Chemical composition and biological activities of the aqueous fraction of Parkinsonea aculeata L. growing in Saudi Arabia. Arab J Chem. 10.1016/j.arabjc.2018.08.003 DOI: 10.1016/j.arabjc.2018.08.003
Barros L, Dueñas M, Alves CT, Silva S, Henriques M, Santos-Buelga C, Ferreira ICFR (2013) Antifungal activity and detailed chemical characterization of Cistus ladanifer phenolic extracts. Ind Crops Prod. 10.1016/j.indcrop.2012.03.038 DOI: 10.1016/j.indcrop.2012.03.038
Giusti MM, Rodríguez-Saona LE, Griffin D, Wrolstad RE (1999) Electrospray and tandem mass spectroscopy as tools for anthocyanin characterization. J Agric Food Chem. 10.1021/jf981242+ DOI: 10.1021/jf981242+
Fernández-Agulló A, Freire MS, González-Álvarez J (2015) Effect of the extraction technique on the recovery of bioactive compounds from eucalyptus (Eucalyptus globulus) wood industrial wastes. Ind Crops Prod. 10.1016/j.indcrop.2014.11.031 DOI: 10.1016/j.indcrop.2014.11.031
Tahara K, Nishiguchi M, Frolov A, Mittasch J, Milkowski C (2018) Identification of UDP glucosyltransferases from the aluminum-resistant tree Eucalyptus camaldulensis forming β-glucogallin, the precursor of hydrolyzable tannins. Phytochemistry. 10.1016/j.phytochem.2018.05.005 DOI: 10.1016/j.phytochem.2018.05.005
