Phytochemical Screening and Gas Chromatography-Mass Spectrometry (GC-MS) Analysis of the Fermented Maize Aqueous Extract of Enantia Chlorantha Stem Bark

Phytochemical Screening and Gas Chromatography-Mass Spectrometry (GC-MS) Analysis of the Fermented Maize Aqueous Extract of Enantia Chlorantha Stem Bark

^1*Gabriel A. Sotade, ²E. Chukwu Onyeneke, ²Samuel Ifidon Ojeaburu, ³P. Chioma Ofoha, ⁴Rotimi Elijah Abioye, ⁵Victor A. C. Biodun, ⁶Joseph E. Sotade, ¹Jamda D. Ponmak, ⁷Ezekiel O. Salako, ⁸Juliana Sebastian Musa, ⁷Badung Emmanuel Yakubu, ⁹Funmilayo I. Paul, ⁷Emmanuel Joseph, ⁷Johnson D. Olaniyi and ¹⁰Tijani Aniwura

¹Molecular Biology Department, Federal College of Veterinary and Medical Laboratory Technology, Vom, Plateau State, Nigeria

²Biochemistry Department, Faculty of Life Sciences, University of Benin, Benin City, Edo State, Nigeria.

³Medical Biochemistry Department, David Umahi Federal University of Health Sciences, Uburu, Ebonyi State, Nigeria

⁴ICT & Library Division, Planning Department, National Veterinary Research Institute, Vom, Plateau State, Nigeria

⁵Administrative Department, Federal College of Veterinary and Medical Laboratory Technology, Vom, Plateau State, Nigeria

⁶Biotechnology Department, Kings University, Gbongan-Osogbo Road, Odeomu, Osun State, Nigeria

⁷General Studies Department, Federal College of Veterinary and Medical Laboratory Technology, Vom, Plateau State, Nigeria

⁸Parasitology Department, Federal College of Veterinary and Medical Laboratory Technology, Vom, Plateau State, Nigeria

⁹Histopathology Department, Federal College of Veterinary and Medical Laboratory Technology, Vom, Plateau State, Nigeria

¹⁰Computer & ICT Department, Federal College of Veterinary and Medical Laboratory Technology, Vom, Plateau State, Nigeria

^*Corresponding Author

DOI: https://doi.org/10.51244/IJRSI.2025.12010043

Received: 24 December 2024; Accepted: 28 December 2024; Published: 10 February 2025

ABSTRACT

Enantia chlorantha (EC) is sought after by the rural communities in South Western Nigeria and some other African countries for the treatment of many ailments. Despite its widespread use, the phytochemical and the Gas Chromatography-Mass Spectrometry (GC-MS) screening of the fermented maize aqueous extract remain undetermined. This study was carried out with the aim to evaluate the phytochemical and GC-MS analysis of the plant stem bark. The phytochemical screening was carried out using standard methods while the identification and the quantification of the bioactive components were determined by GC-MS single-phase ion mode and the spectra from the detected compounds were matched with known compounds of the National Institute of Standards and Technology (NIST). The qualitative phytochemical screening revealed the presence of alkaloids, cardiac glycosides, flavonoids and steroids in the extracts. Thirty-seven (37) bioactive chemical constituents were identified by GC-MS. Out of these, thirty-one (31) were fatty acids and its derivatives. These bioactive constituents include Oleic acid (29.98%), n-Hexadecanoic acid (18.59 %), Eicosanoic acid (7.34%), 2-Methyl-4-(2,6,6-trimethyl-1-cyclohexen–1-yl)-2-butenal (6.03%) and 17-(acetyloxy)-, (4. beta.)- 18-Oxokauran-17-yl acetate Kauran-18-al (3.19%) as the predominant. The study revealed that the fermented maize aqueous extract of E. chlorantha stem bark have appreciable amount of pharmacologically important phytochemicals and the bioactive chemical constituents present in the extract may also serve as potential drug target for drug discovery and development. Fermented maize water may also be used as solvent of choice apart from water and alcohol.

Keywords: Enantia chlorantha; phytochemical screening; fermented maize water; eicosanoic acid.

INTRODUCTION

Enantia chlorantha (EC) is an ornamental tree that may grow up to 30 m high, with dense foliage and spreading crown. The plant extracts (especially aqueous and ethanolic extracts) have been widely used in folk medicine for the treatment of a large number of human ailments especially in rural communities in South Western Nigeria. The stem bark is mostly preferred (even though the roots and the leaves may also be used), and decoctions, tinctures or infusions may be prepared.

In Cameroon, the stem bark extract of E. chlorantha is used to treat jaundice and urinary tract infections [1]. This is a typical example of the “doctrine of signatures” commonly found in African Traditional Medicine where the colour of a plant part is linked to its ethnomedicinal use [2]. The yellow to orange colour of the plant extracts is due to the presence of the three major water-soluble alkaloids, i.e. palmitine, jathorrizine and columbamine. The herbal preparations of E. chlorantha are usually kept in some households and used often, even without obvious symptoms of malaria, but rather as malaria prophylactics [3].

The knowledge of the phytochemistry of this epoch-making plant species has been greatly utilized in modern medicine and herbal preparations. A number of medicinally useful phytochemicals have been isolated, purified and employed in the prophylaxis and treatment of a myriad of health conditions.

Medicinal plants play an important role in the human health care system [4]. Plants are good sources of biologically active compounds known as phytochemicals. Phytochemicals such as alkaloids, flavonoids, phenolic acids, tannins, terpenoids, lignin, quinones, coumarins, amines, and others found in plants are biologically active and contribute to the antioxidant capacity of the plants in which they are found [5]. In this present study, the qualitative phytochemical screening (Table 1) revealed the presence of alkaloids, cardiac glycosides, flavonoids and steroids. [6] – [9] also reported the presence of these phytochemicals in the stem bark extracts of E. chlorantha.

Phytochemicals are secondary plant metabolites found in various parts of plants; they have diverse roles in plants. These include the provision of vigour to plant; attraction of insects for pollination and feeding, defence against predators and provision of colour while some are simply waste products. A whole range of pharmacological activities have been ascribed to alkaloids which include antimalarial, anticancer [10], antibacterial [11], antitussive, antipyretic, hallucinogenic and antihypertensive [12], anti-hyperglycaemic [13], antiarrhythmic, vasodilatory [14] or as a template for drug discovery [15].

Despite E. chlorantha widespread use, the phytochemical constituents and the bioactive components of the fermented maize aqueous extract remain undetermined to the best of our knowledge. This study investigated the phytochemical and chemical constituents of the fermented maize aqueous extract of Enantia chlorantha stem bark.

MATERIALS AND METHODS

Collection of Plant Materials

The stem bark of Enantia chlorantha used in this study was sourced locally from herb seller and it was immediately labeled with the local name (Awopa or Osupupa or Dokitaigbo in Yoruba, Osomolu in Ikale, Kakerim in Boki) with which it was purchased. The material was identified by a Botanist (UBH- E485) in the Department of Plant Biology and Biotechnology, University of Benin, Benin City, Edo State, Nigeria.

Preparation and Extraction of Plant Materials

The fresh stem bark of E. chlorantha were washed under clean tap water to remove contaminants, debris and dust particles and were cut into pieces after which they were air-dried under shade at room temperature. Thereafter, the dried plant materials were pulverized using an electric blender. One thousand grams (1000 g) of the pulverized stem bark were macerated with 5L fermented maize water under constant stirring for 72 hours [16]. The resulting extract was filtered using Whatman No.42 filter paper (125 mm) into clean containers. The filtrate was concentrated using a freeze dryer at the National Centre for Energy and Environment, University of Benin, Benin City and the extract was thereafter stored in sterile containers and kept at 2 – 8 ⁰C till when needed.

Laboratory Preparation of Fermented Maize Water

Three hundred grams (300 g) of yellow corn variety purchased was sorted and pre-washed severally with clean water to remove debris and dust particles. Thereafter, the washed grains were subjected to 48 hr fermentation under aseptic measures according to the modified method of [17]. The grains were steeped in sterile stainless steel container with cover. At every 12 hr, the steeped water was decanted and the fermenting grains were re-washed with warm water (20 – 25 ^oC) and fermented for 48 hr [18]. Thereafter, the grains were drained, ground with hand mill and sieved with muslin cloth. The recovered waste was further subjected to 24 hr fermentation, after which it was milled and sieved. The resulting filtrate was utilized as fermented maize water.

Phytochemical Screening of the Fermented Maize Aqueous Extract of Echlorantha Stem Bark

The preliminary phytochemical screening to detect the presence of secondary metabolites such as alkaloids, tannins, steroids, flavonoids, anthraquinones was carried out using standard procedures as described by Harborne [19], [20].

GC-MS Analysis of the Fermented Maize Aqueous Extract of E. chlorantha Stem Bark

The analysis of the fermented maize aqueous extract was carried out using Agilent Technologies 7890A coupled with Agilent Technologies 5975CVL MSD, the carrier gas (mobile phase) was helium with linear velocity of 1 ml/min while the stationary phase was the column Agilent technology HP5 MS with length 30m, internal diameter of 0.320 mm and thickness of 0.25 microns. The volume of the sample injected was 1 µL, oven initial temperature was 80 °C to hold for 2 minutes and the final temperature of 240 ⁰C to hold for 10 minutes. The data was processed with Shimadzu’s LabSolutions software V4.3. Compounds identified were compared with the compounds in the National Institute of Standard and Technology database. The retention time, name, molecular weight, molecular formula, and percent peak area were determined for each compound. The identification of the components in the extract was based on the comparison of their mass spectra and the retention time with the literature data and by computer matching with the NIST and WILEY Mass Spectra libraries as well as by comparison of the fragmentation pattern of the mass spectra data with those that are reported in the literature.

RESULTS AND DISCUSSION

The results obtained from the phytochemical composition of the fermented maize aqueous extracts of E. chlorantha stem bark were presented in Table 1. The extract contained alkaloids, cardiac glycosides, flavonoids and steroids while phenols, reducing sugars, saponins, tannins and anthraquinone were not detected.

Table 1: Phytochemical composition of the fermented maize aqueous extracts of E. chlorantha stem bark.

+ = detected; -­ = not detected.

The results of the GC – MS screening of the fermented maize aqueous extract of E. chlorantha stem bark identified thirty-seven (37) bioactive chemical constituents. Out of these, thirty-one (31) were fatty acids and its derivatives. These bioactive compounds have been reported to possess various biological and pharmaceutical activities (Table 2).

Fig. 1.  GC chromatogram of the fermented maize aqueous extract of E. chlorantha stem bark.

Table 2. Compounds isolated from the fermented maize aqueous extract of E. chlorantha stem bark.

RT	Area (%)	Name of Compound	MW	MF	Structures
10.584	1.43	3-methyl-6-(1-methylethylidene) Cyclohexene	136.23	C10H16
11.117	0.35	(4-butylbenzoyl)-o’-(2-methylbenzoyl) 1,2-Benzenediol	388.50	C25H24O4
11.249	2.52	1-ethenyl-1-methyl-2,4-bis (1-methylethenyl) Cyclohexane	204.35	C15H24
11.659	0.38	pentafluoro phenyl 3-Phenylpropionic acid	316.05	C15H9F5O2
12.308	1.65	1-methyl-5-methylene-8-(1-methylethyl) 1,6-Cyclodecadiene	204.35	C15H24
13.042	0.16	3-(6,6 dimethylbicyclo [3.1.1] hept-2-en-2-yl)-, methyl ester 2-Propenoic acid	206.28	C13H18O2
13.201	3.19	17-(acetyloxy)-, (4. beta.)- 18-Oxokauran-17-yl acetate Kauran-18-al	346.51	C22H34O3
13.284	0.92	decahydro-1,1,7-trimethyl-4-methylene 1H-Cycloprop[e]azulen-7-ol	220.35	C15H24O
13.343	1.45	Caryophyllene oxide	220.19	C15H24O
13.432	0.21	5,5-diethyl-3-heptyne	152.28	C11H20
13.541	0.14	diphenyl ester Succinic acid	270.28	C16H14O4
13.613	1.02	1,8-Cyclopentadecadiyne	202.34	C15H22
13.717	0.59	trans-2-Caren-4-ol (essential oil)	152.24	C10H16O
13.869	0.33	hexahydro-4-iodo-4-Iodohexahydro-2(1 H)-pentalenone	250.08	C8H11IO
13.952	0.33	2,5,5-trimethyl- 1,3,6-Heptatriene	136.23	C10H16
14.035	1.04	N-(4-methylbenzoyl)-, hexyl ester D-Alanine	305.41	C18H27NO3
14.276	0.80	6-Isopropenyl-4,8a-dimethyl-1,2,3,5,6,7,8,8a-octahydro-naphthalen-2-ol	220.40	C15H24O
14.347	0.80	(Z, Z)-. alpha. –Farnesene	204.35	C15H24
14.706	0.85	1-methoxymethyl-1-(Methoxymethyl)decahydronaphthalene Decalin	182.16	C12H22O
14.882	2.00	3-cyclopentyl-6-methyl 3,4-Heptadien-2-one	192.29	C13H20O
14.983	0.77	1-Cyclohexene-1-acetaldehyde, alpha.,2-dimethyl- 2-(2-Methyl-1-cyclohexen-1-yl) propanal	152.24	C10H16O
15.141	0.55	1-Cyclohexene-1-acetaldehyde, alpha.,2-dimethyl- 2-(2-Methyl-1-cyclohexen-1-yl) propanal	152.24	C10H16O
15.211	0.72	2,4-Dimethyl-3-nitrobicyclo[3.2.1]octan-8-one	197.23	C10H15NO3
15.351	0.30	3-Furancarboxylic acid, 2,5-dimethyl-, hydrazide	154.17	C7H10N2O2
15.401	6.03	2-methyl-4-(2,6,6-trimethyl-1- cyclohexen-1-yl) -(2E)-2-Methyl-4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2-butenal	206.32	C14H22O
15.719	1.55	Spiro-6-(bicyclo [3.2.1] octane)-2′-(oxirane)	254.37	C15H26O3
15.902	0.85	2,2-Dimethylocta-3,4-dienal	152.24	C10H16O
16.125	18.59	n-Hexadecanoic acid	256.42	C16H32O2
16.867	0.39	5-methyl-3-octyne	124.22	C9H16
17.288	29.98	Oleic Acid	282.50	C18H34O2
17.393	7.34	Eicosanoic acid	312.53	C20H40O2
18.152	1.54	3-methyl-3-1,2-Cyclopentanediol	116.16	C6H12O2
19.153	2.69	1-Docosene	308.58	C22H44

RT = retention time; MW = molecular weight; MF = molecular formula; BHT = butylated hydroxytoluene; SDS-PAGE = Sodium Dodecyl Sulphate-Polyacrylamide Gel Electrophoresis.

The presence of alkaloids in the plant extracts as shown in Table 1 is in agreement with the previous study carried out by [21] on phytochemical analysis of E. chlorantha stem bark. The presence of phytochemicals in medicinal plants is responsible for their activities in the treatment of diseases [22]. The high content of alkaloids as observed in this present study contributed to the bitter taste of the extracts because alkaloids are very alkalic.

Cardiac glycosides are majorly used in the treatment of cardiac arrhythmia and congestive heart failure, whereby they inhibit Na⁺/K⁺-ATPase pump that usually causes positive ionotropic effects and electrophysiological changes [23], [24] while the presence of flavonoids in the stem bark might be responsible for the use of this plant for the treatment of malaria and cough.

Gas chromatography-mass spectrometry (GC–MS) analysis of the fermented maize aqueous extract of E. chlorantha stem bark revealed the presence of thirty-seven (37) bioactive compounds. The relative abundant bioactive compounds in the fermented maize aqueous extract of E. chlorantha was in the order Oleic acid (29.98%) > n-Hexadecanoic acid (18.59 %) > Eicosanoic acid (7.34%) > 2-Methyl-4-(2,6,6-trimethyl-1-cyclohexen–1-yl)-2-butenal (6.03%) > 17-(acetyloxy)-, (4. beta.)- 18-Oxokauran-17-yl acetate Kauran-18-al (3.19%).

From the literature, these bioactive compounds play crucial roles in homeostasis and the general metabolism of the human body. Oleic acid was reported to have anaemiagenic, anti-androgenic, anti-inflammatory, choleretic, anti-cancer, dermatitigenic and antibacterial properties and prevent insect pests [25], [26]. n-Hexadecanoic acid has anti-inflammatory, antioxidant, anti-androgenic, hypocholesterolaemic properties, acts as an haemolytic inhibitor [27] and potent mosquito larvicide [28] while Eicosanoids are potent lipid mediators that are involved in many central physiological processes such as parturition, haemostasis and renal function [29].

CONCLUSION

The results of the phytochemical screening revealed that the fermented maize aqueous extract of E. chlorantha stem bark have appreciable amount of pharmacologically important phytochemicals and the bioactive chemical constituents present in the extract may also serve as potential drug target for drug discovery and development. Fermented maize water may also be used as solvent of choice apart from water and alcohol.

Further studies should be carried out at molecular level to isolate and characterize the pure compounds responsible for all these activities.

REFERENCES

1. Adjanohoun, J. E., Aboubakar, N., Dramane, K., Ebot, M. E., Ekpere, J. A., Enoworock, E. G., Focho, D., Gbile, Z. O., Kamanyi, A., Kamsu, K. J., Keita, A., Mbenkum, T., Mbi, C. N., Mbiele, A. C., Mbome, J. C., Muberu, N. K., Nancy, W. L., Kongmeneck, B., Satabie, B., Sowora, A., Tamze, V. and Wirmum, C. K. (1996). Traditional Medicine and Pharmacopoeia: Contribution to ethno botanical and floristic studies in Cameroon. Organization of African Unity; Scientific, Technical and Research Commission. Centre National de Production de Manuels Scolaires (CNPMS), Porto Novo, Benin.
2. Bennett, B. C. (2007). Doctrine of signatures: an explanation of medicinal plant discovery or dissemination of knowledge? Economic Botany. 61(3): 246 – 255.
3. Ishola, N. O., Oreagba, I. A., Adeneye, A. A., Adirije, C., Oshikoya, K. A. and Ogunleye, O. O. (2014). Ethnopharmacological survey of herbal treatment of malaria in Lagos, Southwest Nigeria. Journal of Herbal Medicine. 4: 224 – 234.
4. Bonini, S. A., Premoli, M., Tambaro, S., Kumar, A., Maccarinelli, G., Memo, M. and Mastinu, A. (2018). Cannabis sativa: A comprehensive ethanopharmacological review of a medicinal plant with a long history. Journal of Ethnopharmacology. 227: 300 – 315.
5. Gulcin, I., Topal, F., Ozturk Sarikaya, S. B., Bursal, E., Birsel, G. and Goren, A. C. (2011). Polyphenol contents and antioxidant properties of Medlar (Mespilus germanica L). Records of Natural Products Journal. 5: 158 – 175.
6. Bassey, A. L., Nwafor, P. A., Udobang, J. A. and Ettebong, E. O. (2017). Subchronic evaluation of the ethanol stem bark extract of Enantiachlorantha in rodents biochemical, haematological evaluation and effect on body weight. World Journal of Pharmaceutical Research. 6(9): 73 – 83.
7. Nurain, I. O., Bewaji, C. O., Abubakar, A. A., Mustapha, A., Ajani, E. O., Sabiu, S., Usman, L. A., Abdulhameed, H. A. and Ahmed, S. B. (2018). Antimalarial and reno-protective potentials of combined stem bark extracts of Khaya grandifoliola and Enantia chlorantha in Plasmodium infected mice. Iranian Journal of Toxicology. 12(3): 29 – 37.
8. Abubakar, A., Ahmad, N. S., Akanya, H. O., Abdulkadir, A. and Abubakar, A. N. (2020). Antiplasmodial activity of total alkaloids and flavonoids of stem bark extracts of Enantia chlorantha in mice. Comparative Clinical Pathology. 29: 873 – 881.
9. Ibrahim, L. B., Idowu, P. F., Moses, O. A., Alabi, M. A. and Ajani, E. O. (2021). Antidiabetic potential of stem bark extract of Enantia chlorantha and lack of modulation of its therapeutic efficacy in diabetic rats co-administered with lisinopril. Acta Chimica Slovenica. 68: 118 – 127.
10. Kittakoop, P., Mahidol, C. and Ruchirawat, S. (2014). Alkaloids as important scaffolds in therapeutic drugs for the treatments of cancer, tuberculosis and smoking cessation. Current Topics in Medicinal Chemistry. 14(2): 239 – 252.
11. Cushnie, T. P., Cushnie, B. and Lamb, A. J. (2014). Alkaloids: An overview of their antibacterial, antibiotic enhancing and antivirulence activities. International Journal of Antimicrobial Agents. 44(5): 377 – 386.
12. Hesse, M., Thylstrup, B. and Skogen, J. C. (2022). Commentary on Chai et al: Drug use, self-harm, suicide, and use of registry data in epidemiological research. Addiction. 117: 1950 – 1951.
13. Qui, S., Sun, H., Zhang, A., Xu, H. and Wand, X. (2014). Natural product alkaloids: Basic aspects, biological roles and future perspective. Chinese Journal of Natural Medicines. 12(6): 401 – 406.
14. Sinatra, R. S., Jahr, J. S. and Watkins-Pitchford, J. M. (2010). The essence of analgesia and analgesics. Cambridge: Cambridge University Press. 82 – 90.
15. Pérez-Amador, M. C., Muñoz Ocotero, V., García, J. M., Castañeda, A. R. and González, E. (2007). Alkaloids in Solanum torvum (Solanaceae). International Journal of Experimental Botany. 76: 39 – 45.
16. Sotade, G. A., Ojeaburu, S. I., Onimisi, O. S. A., Otokiti, A. U., Duile, P. T., Azees, A. S., Abioye, R. E. and Biodun, V. A. C. (2024). “Proximate, phytochemical and gas chromatography-mass spectrometry (GC-MS) analysis of the carbonated drink (Soft Drink) extract of Enantia chlorantha stem bark”. Asian Journal of Physical and Chemical Sciences. 12 (2): 34 – 53.
17. George-Okafor, U. O., Taise, F. O. and Anosike, E. E. (2007). Influence of corn steeping on fermented mash (Akamu). In: Proceedings of workshop on Workshop on Biotechnology and Nigeria’s Industrial Development at Enugu, Nigeria. Pp. 18 – 26.
18. Akunkee, R. E. (1973). Malo-lactic fermentation and wine making. In: The Chemistry of Wine Making. Webb, A. D. (e.d.). American Chemical Society, Washington, D. C. p.514.
19. Harborne, J. B. Phytochemical methods, Chapman and Hall, London. 3rd edition. 1998; 88 – 98.
20. Trease, G. E, Evans WC. Pharmacognosy. 15th edition. WB Saunders Company Limited. U.K. 2002; 585.
21. Ayoade, A. A, and Akanji, M. A. (2010). Antimalarial bioactivity of Enantiachlorantha stembark in medicinal plants. The Journal of Phytopharmacology. 1: 441 – 447.
22. Dubey, N. K. (2014). Plants as a source of natural antioxidants. Seerapt, J., Alexandra, L., & Shankari,W. (Editors). Croydon, U.K, CPI group Ltd, 6 – 10.
23. Ngoci, S. N., Matasyoh, J. C., Mwaniki, C. G. and Mwendia, C. M. (2011). Phytochemical and cytotoxicity testing of Indigofera lupatana Baker F. Journal of Animal and Plant Sciences. 11(1): 1364 – 1373.
24. Ifemeje, J. C., Egbuna, C. S., Eziokwudiano, J. O. and Ezebao, F. C. (2014). Determination of the anti-nutrient of composition of Ozimum grassinum. International Journal of Innovation and Science Research. 3(2): 127 – 133.
25. Jang, J. S., Yang, Y. C., Choi, D. S. and Ahn, Y. J. (2005). Vapor phase toxicity of marjoram oil compounds and their related monoterpenoids to Blattella germanica (Orthoptera: Blattellidae), Journal of Agricultural and Food Chemistry. 53(20): 7892 – 7898, doi: 10.1021/jf051127g.
26. Awa, E. P., Ibrahim, S. and Ameh, D. A. (2012). GC-MS analysis and antimicrobial activity of diethyl ether fraction of methanolic extract from the stem bark of Annona senegalensis Pers. International Journal of Pharmaceutical Sciences and Research. 3: 4213 – 4218.
27. Kumar, S. P. J., Prada, S. R., Banerjee, R. and Thammineni, C. (2015). Seed birth to death: dual functions of reactive oxygen species in seed physiology. Annals of Botany. 116(4): 663 – 668.
28. Rahuman, A. A., Gopalakrishnan, G., Ghouse, B. S., Arumugam, S. and Himalayan, B. (2000). Effects of Feronia limonia on mosquito larvae. Fitoterapia. 71: 553 – 555.
29. Thulasingam, M. and Haeggström, J. Z. (2020). Integral Membrane Enzymes in Eicosanoid Metabolism: Structures, Mechanisms and Inhibitor Design. Journal of Molecular Biology, 432(18): 4999 – 5022.