Ewé: The Plant Knowledge

Ewé mean leaf, and na him stand for the whole plant part of Yoruba medicine. How the system take summarize itself na the proverb ewé ni oògùn, leaf na medicine, and the claim wey match am inside Ifá literature say no plant dey wey no be medicine. The size of wetin dem document plenty well well: Pierre Verger Ewé, wey be the standard reference, record information on top about three thousand five hundred plants wey dem gather over forty years of fieldwork, plus more than two thousand remedies, the plant parts wey dem use, how dem take prepare am, the incantations wey follow dem, and how dem connect to Ifá divination signs 12.

This file dey do two things. E dey describe how dem arrange the knowledge, how dem name am and remember am, wey be where the tradition distinct pass and where people understand least. Then e come put one worked table of named plants against the pharmacological literature, dey mark for each one wetin dem don actually prove, inside which model, and wetin dem never prove.

Warning about the table before the table: the honest answer for most of the pharmacopoeia na say nobody don check am. That one no be verdict on top the tradition. Na just statement about where research funding go.

Verger's corpus

Pierre Fatumbi Verger (1902-1996) na French photographer and ethnographer wey settle for Bahia, dem initiate am as babaláwo, e take the name Fatumbi, and e spend decades dey travel between Brazil and Yorubaland. Ewé: The Use of Plants in Yoruba Society come out for 1995, e reach 744 pages, and na the single biggest published record of Yoruba plant knowledge 1.

Wetin make am special no be the list of species. Na say Verger record the plants together with the ọ̀fọ̀, the incantations, and with the odù Ifá wey the formulae attach to 2. Most ethnobotany dey record plant, wetin dem dey use am for, and how dem dey prepare am. Verger record the plant inside the spoken and divinatory apparatus wey practitioner dey actually use am inside, wey make the book be source for the structure of the knowledge and no be only for the content.

Two cautions about using am.

Na record of wetin practitioners talk, no be pharmacological evaluation. Verger document; e no test. Any use wey dem record inside Ewé na evidence say the use dey traditional, wey be real and valuable thing to establish, and e no be evidence say the medicine dey work.

The publication get controversy among practitioners. Plenti of the material na secret under obligation, and to put am for print, some people see am as breach while other people see am as rescue. People wey dem initiate hold the two positions, and this compiler no dey judge between dem. The tension na the same one wey dey run through all publication of initiate knowledge and e dey show again for 05-ifa.

How plants are classified

Classification wey dey use pass one and dem dey work for different levels. Reader no suppose expect single Linnaean-style hierarchy, because no be wetin the system dey for be that.

By element. One documented scheme dey divide leaves into four groups: ewé afẹ́fẹ́, leaves of air or wind; ewé iná, leaves of fire; ewé omi, leaves of water; and ewé ilẹ̀ or ewé igbó, leaves of the ground or of the forest 3. Schemes dey vary by source and by practitioner lineage, and 06-orisa/11-osanyin treat this one alongside Ọ̀sanyìn, the òrìṣà wey hold the knowledge of leaves.

By sensory property. Herbalists wey dey work dey identify and group plants by smell, by how the leaf feel, by how the plant dey react when touch am, and by the sensation wey person feel when e touch am. These properties dey enter naming as well as classification, wey be the link to the next section.

By action. The functional grouping wey matter pass for practice: wetin plant dey do. Bitter taste particularly na recognised class marker, and e map enter the kòkòrò and aràn framework wey dem describe inside file 01, where bitter-tasting plants na the characteristic agents to control the organisms wey dem hold responsible for disease.

By òrìṣà. Plants dey attach to deities, and preparation for condition wey particular òrìṣà dey control dey draw from that òrìṣà's plants.

These things dey cross each other. Plant get element, set of sensory properties, set of actions, and set of divine associations all at once, and practitioner dey use whichever angle the problem need. That one na working classification instead of taxonomy, and to judge am against Linnaeus dey mistake wetin e dey do.

The name as mnemonic: the wordplay that carries the pharmacopoeia

Na this feature distinct pass for Yoruba pharmacological memory, and e dey common say people dey either ignore am or turn am to mystery. The finding na from Buckley, through fieldwork with herbalists: most medicinal incantations dey use one form of wordplay, wey resemble punning, to bring out the properties of the plants wey the name of the plant dey imply 4. Verger material dey organized around this same relationship 2.

See wetin that one mean mechanically. Yoruba na tonal language wey get heavy homophony, and plenti plant names dey clearly compound or descriptive. Incantation over preparation dey take the plant name and pun on am, so that the name go come talk wetin the medicine suppose do. Some worked examples of the naming logic, at the level wey published sources support:

Ewé ìṣẹ́nbáyé. The name of plant frequently na compressed sentence. Names wey take the form a-...-bá-... or wey dem build on verbs of doing and arriving dey common, and the incantation dey extract the verb.

Dòkítà igbó, forest doctor, na Yoruba name for Enantia chlorantha 5. That name no be mnemonic pun but direct claim about the position of the plant, and e dey tell you say the plant dey important before any chemistry talk am.

Ewúro, Vernonia amygdalina, bitter leaf. The name dey mark the property wey classify am.

Dòngòyárò for Azadirachta indica, neem. The name na borrowed word wey show how the plant take reach West Africa during colonial period, and e dey serve as useful reminder say the pharmacopoeia no be closed ancient list. Neem enter for nineteenth and twentieth century, and Yoruba practice absorb am, give am name, and find work for am. Tradition dey accept new material.

Two things come out from this naming system and the two of dem matter.

Na memory technology. For system wey no get writing, to link how dem dey use plant to the name mean say the practitioner wey know the name get hook to the use. The incantation na the way to recall the knowledge and e still be the thing wey dey activate am. This one na solid solution to the problem of keeping several thousand plant-and-use pairs for memory, and na im make the pharmacopoeia big reach like this.

E dey create systematic risk of false positives. If wetin plant dey do come from wordplay on top the name, e mean say na the name bring some uses out instead of say dem discover am through observation. The same mechanism wey make the knowledge easy to remember dey also create indications wey sound like truth but no get any empirical basis backing dem. This na the single most important thing to understand about the epistemic status of the pharmacopoeia, and e divide exactly the way the evidence for the table below show: some plants get real activity wey practitioners see without any laboratory, while some get indications wey be just artefact of Yoruba phonology. Na only testing fit separate the two, and na testing be wetin dem mostly never do.

To talk this thing plain no mean say person dey dismiss am. Signature-based reasoning bring plenty indications for European herbalism too, and European herbalism still bring out digitalis and salicylate. The main point na say, just because use dey inside tradition no mean say e dey work well on its own, e only be strong evidence say the use na traditional thing.

The scale of the pharmacopoeia

The roughly 3,549 plants and over 2,000 remedies wey Verger record na the biggest figure 12. Today ethnobotanical surveys dey record smaller local pharmacopoeias, wey be wetin person go expect since dem dey check only one town or district instead of the whole tradition: one survey of Ile-Ife record 87 species for 43 families from 70 informants 6. Bigger list of Yoruba useful plants across southwestern Nigeria don show for Heliyon 7.

Two features for the survey literature make sense to mention because dem touch the question of whether this na systematic knowledge or individual improvisation.

Agreement between independent practitioners dey high for the species wey dem dey use well. For places wey dem calculate quantitative indices, small number of species dey repeat across informants with high citation frequency, wey show how transmitted systematic knowledge dey look like, no be how individual invention dey look.

Leaves dey lead. Across surveys, na leaf be the plant part wey dem dey use pass by far, wey match the way ewé dey stand for the whole field, and herbs plus shrubs plenty pass trees for the counts.

Warning on top research integrity. One quantitative ethnobotany paper about Ile-Ife wey people dey cite well well, wey dem publish for Evidence-Based Complementary and Alternative Medicine for 2021, the publisher later retract am after investigation find evidence say dem systematically manipulate the publication and peer-review process 6. The numbers still dey circulate well for later literature wey cite am. This work dey report the figures only with the retraction attached, and reader wey dey see Nigerian ethnobotany citations suppose know say the Hindawi retraction wave of 2023 remove plenty papers for this field.

The table

Wetin follow na worked table of named plants. Dem grade the evidence column with purpose, and each grade get specific meaning:

• Human trial evidence mean say at least one controlled trial happen for human beings, with the result clearly stated whether e positive, negative, or inconclusive.
• Animal or in vitro only mean say activity don show for model, and dem name the compound where dem isolate one. This one no establish clinical efficacy.
• Compound isolated, activity uncharacterised mean say dem don do chemistry but therapeutic activity never dey established.
• Traditional use only mean say dem no see any pharmacological evaluation for the specific traditional indication. Na this category common pass for the pharmacopoeia as a whole, and e no plenty reach for this table, because the table pick plants wey dem don study.

The table no be therapeutic guide and nothing inside am suppose dey read as recommendation. Doses for traditional use no dey standardised, extracts inside studies no be the same material as traditional preparations, and many of these plants dey toxic at doses wey person fit easily take.

Yoruba name	Botanical binomial	Traditional use	Wetin research don establish	Grade
Dòkítà igbó, awópa	Enantia chlorantha Oliv. (Annonaceae)	Malaria, fever, jaundice; one of di Yoruba medicine for malaria wey dem dey cite pass	Protoberberine alkaloids dey inside; dem report say di alkaloid jatrorrhizine get ED50 of 0.34 mg/g ethanolic and 6.9 mg/g aqueous extract against Plasmodium yoelii 8. Toxicological study of di purified protoberberine alkaloidal fraction for 120 mice no find any damage (pathological lesions) for stomach, kidney, oesophagus or liver at di doses wey dem test, e cause mild to moderate lung oedema, and no significant biochemical differences from control, wey show say e relatively safe for short-term use 9	Animal and in vitro only
Òrúwo	Morinda lucida Benth. (Rubiaceae)	Malaria, fever, jaundice	Bioassay-guided isolation identify antimalarial triterpenoid acids wey include asperulosidic acid and asperuloside; dem report say parasitaemia drop by 51.52 percent against P. berghei NK65 and chemosuppression dey between 39.8 to 90.5 percent 8. One 2023 study on leaf combination report 90.7 to 91.0 percent chemosuppression at 16 mg/kg for two-plant combinations compared to chloroquine wey be 100 percent at 10 mg/kg, and molecular docking identify oleanolic acid and ursolic acid as multiple-target inhibitors 10	Animal and in vitro only
Awùn, àhun	Alstonia boonei De Wild. (Apocynaceae)	Malaria, fever, pain, snakebite	Dem report chemosuppression wey dey between 0.2 to 74.8 percent for mice wey get P. berghei 8. Di wide range across studies na di main finding itself: di plant material no dey reliably potent under di conditions wey dem test	Animal and in vitro only, inconsistent
Dòngòyárò	Azadirachta indica A. Juss. (Meliaceae)	Malaria, fever, skin conditions; plant wey enter during colonial time wey come join di pharmacopoeia	Pass 400 compounds dem don isolate from di plant, including azadirachtin, nimbidin, nimbin, nimbolide and gedunin 11. Dem identify gedunin say e get antiplasmodial property, with dose-dependent suppression wey reach 69.65 to 78.32 percent 8; bioassay-guided work on di fruits confirm strong in vitro antiplasmodial activity for gedunin and azadirone and identify two new triterpenoids, neemfruitins A and B 12	Animal and in vitro only
Kóóko oyinbo	Cymbopogon citratus (DC.) Stapf (Poaceae)	Fever, malaria, dem dey drink am as tea (infusion)	Dem identify geranial for inside di essential oil; dem report IC50 of 4.2 micrograms per millilitre against P. falciparum 8	In vitro only
Ewúro	Vernonia amygdalina Delile (Asteraceae)	Malaria, fever, stomach wahala, diabetes; dem also dey chop am as food	Plenty published research dey on antimalarial and antidiabetic screening for animal and in vitro models. Dis compiler no find any controlled clinical trial for human being for malaria indication	Animal and in vitro only
Orógbó	Garcinia kola Heckel (Clusiaceae)	Dem dey chew am for cough, chest and throat wahala, as stimulant, and for liver conditions	Dem isolate and characterise di biflavonoid complex kolaviron, wey get GB1, GB2 and kolaflavanone inside; dem also find garcinoic acid, garcinal, kolanone, gakolanone 13. Research on rodent models document hepatoprotective, cardioprotective, neuroprotective, anti-inflammatory, antidiabetic and antimalarial activity 13. One randomised human trial for knee osteoarthritis dey 14. Di 2023 critical review state say clinical data for human beings on any component of G. kola completely dey missing, say most studies use doses above 100 to 400 mg/kg wey no clinically realistic and correspond roughly to 7 to 14 g of pure substance in a human, say very few studies use proper controls, and say positive controls wey dem use often dey around one hundredth of di kolaviron dose 13	Animal models plus one human trial; di review literature conclude say human evidence base no dey
Ẹfinrin, ẹfinrin nla	Ocimum gratissimum L. (Lamiaceae)	Fever, diarrhoea, skin infections, infertility, dem dey drink am as leaf decoction	Eugenol na di major essential-oil constituent, wey reach 74.83 percent for one analysis; dem also identify thymol, carvacrol, limonene, beta-caryophyllene, rosmarinic acid, caffeic acid, quercetin and luteolin 15. Antioxidant, anti-inflammatory, antimicrobial, antidiabetic, hepatoprotective, analgesic and neuroprotective activity dey documented for animal and in vitro work. Di 2021 review state clearly say dem need further human clinical trials to establish effective and safe doses, and e no find any human trials 15	Animal and in vitro only
Ẹ̀gbọ̀, ìbẹ̀pẹ	Carica papaya L. (Caricaceae)	Leaf extract for fever and, as people dey use am widely across di tropics today, for low platelets for dengue	Dem do meta-analysis for nine controlled trials. Seven show increase for platelet counts; mean improvement for platelet count between day one and day five na 35.45 (95% CI 23.74 to 47.15, three studies, 129 participants, graded as low quality evidence); possible reduction for hospital stay of 1.98 days (95% CI 1.83 to 2.12, three studies, 580 participants, low quality). Di authors conclude say wetin dey on ground now no reach to comment on di role of di extract for dengue, because di clinical value of platelet rise wey no get clearer outcome measures never clear 16	Human trial evidence, low quality, inconclusive
Ejinrin wéwé	Momordica charantia L. (Cucurbitaceae)	Diabetes, fever, worms	Randomised placebo-controlled trial for type 2 diabetes, 90 subjects dem analyse for 12 weeks: HbA1c no change for di two groups; mean fasting glucose drop for di extract group (p = 0.014); no serious adverse events 17. So: e get measurable effect on fasting glucose, but no effect on di standard measure of glycaemic control	Human trial evidence, mixed
Àsọ̀fẹ́yẹjẹ, ìra	Rauvolfia vomitoria Afzel. (Apocynaceae)	Mental disturbance, agitation, hypertension, snakebite	Dis genus na di source of monoterpene indole alkaloids like reserpine, ajmaline, ajmalicine, serpentine and yohimbine 18. Dem develop reserpine into mainstream antihypertensive and early antipsychotic, and clinical trials dey for R. serpentina formulations and for di alkaloids themselves; for R. vomitoria specifically, di review note say di extracts and constituents dey await clinical investigation 18. Dis na di clearest case for Yoruba pharmacopoeia where di traditional indication, agitation and high blood pressure, match di pharmacology of one isolated compound wey enter world medicine	Compound isolated and clinically developed as a single agent; dem never test di plant itself as dem dey use am traditionally
Èlú	Philenoptera cyanescens (Schumach. & Thonn.) Roberty, formerly Lonchocarpus cyanescens (Fabaceae)	Indigo dye; dem also dey use am traditionally for skin conditions and as wash	Chemistry of di dye well characterised: indigotin plus 2-hydroxynaphthoquinone and mineral ions. Dem treat di dyeing chemistry for file 09 and 07-arts/05-textiles. No study wey dem find evaluate di medicinal indications	Traditional use only for di medicinal indication
Tagìrì	Adenopus breviflorus Benth., now Lagenaria breviflora (Cucurbitaceae)	Dem dey put am round di house make smallpox and measles no spread; na prophylactic rather than treatment 19	No study wey dem find evaluate di prophylactic claim. As physical barrier against airborne virus, di claim no get plausible mechanism	Traditional use only
Ewé àbámọ̀dá	Bryophyllum pinnatum (Lam.) Oken (Crassulaceae)	Dem dey rub am for wounds and boils, and dey take am for different complaints	Dem isolate bufadienolides from di genus and characterise am; dis ones na cardiac-active steroids and di toxicological significance na real tin	Compound isolated; traditional indications not established
Ataare	Aframomum melegueta K.Schum. (Zingiberaceae)	Grains of paradise; ritual use for prayer and offering, also for digestion and as stimulant	Substantial phytochemical and pharmacological literature dey for animal and in vitro models. No human trial dem find for di traditional indications	Animal and in vitro only
Àgbálùmọ̀	Chrysophyllum albidum G.Don (Sapotaceae)	Dem dey chop di fruit; dem dey use di bark and leaf for different complaints	Lab models document antioxidant and related activity	Animal and in vitro only
Èèrù	Xylopia aethiopica (Dunal) A.Rich. (Annonaceae)	Post-partum preparations, digestive complaints, spice	Pharmacological screening published for animal and in vitro models	Animal and in vitro only
Egúsí, ẹ̀wọ̀n	Nauclea latifolia Sm., now Sarcocephalus latifolius (Rubiaceae)	Malaria, fever, pain	Indole alkaloids dem isolate from di species; dis genus dey among di ones wey get bioguided attention pass within sub-Saharan Rubiaceae, with screening for antimalarial, antimicrobial, antihypertensive, antidiabetic, antioxidant and anti-inflammatory activities 20	Animal and in vitro only

To read di table honestly

Four conclusions follow, and person suppose hold dem together.

Di plant dem pick na true most times. Di practitioners pick plants wey get compounds wey get active power wey person fit measure, and dem do am without microscope, cell culture, animal models, or chemistry. Dis one na proper knowledge achievement wey deserve make person talk am straight without dodging. Di antimalarial group na di strongest example, and wetin make am make sense na di two most important malaria medicine for world medicine, quinine from Cinchona and artemisinin from Artemisia annua, wey di two of dem come out from dis exact kind of tradition 8.

If e show activity for lab model, e no mean say e go cure person. Almost all di evidence wey dey above na in vitro or inside rodents. Di extracts no dey standardized, di strength dey change well well according to di plant material and how dem extract am, and di dose wey dey work for animals most times na dose wey no human being go fit take. Di Garcinia kola review talk dis point with serious power and accuracy, and di criticism fit apply to di whole field 13.

For where human trials dey, di results small and e mix. Carica papaya dey increase platelet count for dengue fever based on low-quality evidence, without any clear proof say e dey affect di main health outcomes wey matter 16. Momordica charantia dey bring fasting glucose down but e no touch HbA1c 17. Dis na how honest reading of human evidence be, and e no mean say di tradition win or say e fail completely.

Say evidence no dey mostly mean say research no dey. For majority of di thousands of plants wey Verger record, and for most sickness wey no be malaria, pharmacological evaluation no dey at all. Di research work face where funding dey. Make reader no use di malaria result conclude say di whole tradition correct, and make dem no use di silence for other sickness conclude say di tradition wrong. Di truth na say dem never study most of dem at all.

Di safety matter also belong here: dis plants no be say dem no get effect, and na dat same property dey make dem potentially useful. Dem don examine abortifacient effect for common African antimalarial plants inside pregnant mice 21, and di matter of contamination and quality problems for today market dey inside file 12.