The “Doctrine of Signatures” in herbal prescriptions in Ikale and Ilaje communities of Ondo State, Southwestern Nigeria

The knowledge and application of the notion of “doctrine of signatures or correspondences” was evaluated among the Ikale and Ilaje people of Ondo State, Southwestern Nigeria. Information was solicited by administering questionnaires to one hundred and five (105) informants. Periodic field observations were also made. The research yielded 60 plants belonging to 37 families. The plants have characteristics such as colour, taste, habit, structure, and appellation which are suggestive of their trado-medical uses. Azadirachtha indica, Petivera alliaceae, Vernonia amygdalina, and Morinda lucida commonly known as “bitters” are used as antimalarial plants. Due to the shape of their fruits/tubers, Kigelia africana and Ipomoea batatas formed part of recipes used in the treatment of breast disorders while others such as Carica papaya and Alstonia boonei are useful as botanical galactogogues. Plants used for magical preparations are also documented. This study confirms the application of the doctrine in plant knowledge and uses. This doctrine can be applied in future bio-prospect and drug development.


INTRODUCTION
The "doctrine of signatures or correspondences" developed in Europe in the 16 th and 17 th centuries, following the collation and consolidation of the body of material that comprised it, asserts that the way plants look, taste, react or are shaped offers strong clues to their medicinal applications (Lev, 2002). This ancient pharmacological theory maintains that similarity between plant habitat or appellation and human features is suggestive of their trado-medical uses. It is believed that these characteristics, commonly called "signatures", are God-given and have possible implications for classification of medicinal plants as well as uses and *Corresponding author. E-mail: kejieconbotunaab@yahoo.com Tel: +234 8138986616; +234 8176124327.
Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License other properties (Saifullahi et al., 2017). Major categories of this doctrine are: 1.) similarity between the shape of the plant organ and the ailing human organ; 2.) similarity between animal shape or behavior to human organ; 3.) similarity of plant colour to the colour of the disease's symptoms; and 4.) similarity of plant characters to human features (Dafni and Lev, 2002). Earlier, Hocking (1977) submitted that the doctrine could be broken down into two chief components which are: 1.) nature has provided in every region plants for remedies which the diseases common to that region require for treatment; and 2.) nature has also provided signs or symbols to indicate by physical characteristics of the drug (colour, shape, taste etc.) the diseases/disorders for which the plant is a remedy.
The Southwestern region of Nigeria is inhabited by people who are particularly rich in customs and traditions. Hence, the Yoruba mythology explains the origin and belief of many cultural concepts in the daily life and practices of the Yorubas (Oso, 1977). This includes the use of plants for the prevention or cure of mild or chronic ailments. Few studies have been conducted in Israel, India, China, and USA (Dafni et al., 1984;Richardson-Boedler, 1999;Dafni and Lev, 2002;Lev, 2002;Bennett, 2007, Kumath, 2015; published information, however, on this concept in Nigeria is scarce and fragmentary.
The aim of this study, being part of a conjunctive focus on indigenous medicines and their furtherance, was to evaluate the knowledge and application of the "doctrine of signatures" among the Ikale and Ilaje people of Ondo State with a view to presenting the plants for biological screening. The doctrine could serve as a reliable basis for future bio-prospect and drug development.

Region and study area
The study was conducted in Ondo State, Southwestern region of Nigeria. Twelve (12) localities in Ikale and Ilaje communities were visited periodically. These areas are occupied majorly by the Ikale and Ilaje-speaking people, other Yorubas (Oyo, Osun, and Ekiti) and Igbira (Edo). The primary economic activity is agriculture. The principal crops are oil palm, plantain and cassava (processed into different food products). Other human activities include fish and vegetable business. Civil servants also inhabit the areas.

Administration of questionnaires
Information about plants was elicited from residents in the areas with the aid of structured questionnaires and personal interview. The purpose of the study was explained to the respondents and informed consent was sought. Only information from willing informants was documented. The questionnaire was divided into two sections. Section 1 was on the demographic variables of respondents while section 2 evaluated informants' knowledge on the characteristics of plants vis-à-vis their supposed uses.
Respondents were cross-questioned to confirm the authenticity of information given. Interview was conducted in the local language (Yoruba, and where necessary the service of an Ikale/Ilaje speaking person was employed). Responses were filled into the questionnaires after each fielded question. The identities of the plants were confirmed using live specimens and reference text (Gbile, 2002); OSUSTECH Herbarium was also consulted. Voucher specimens were deposited in the same herbarium.

RESULTS AND DISCUSSION
Twelve (12) localities were visited. The number of respondents interviewed in the localities was not even because only complete data from willing informants in each locality were documented. The demographic variables of respondents are presented in Table 1. Out of the 105 informants interviewed, 73.33% were males while 26.67% were females. The age of the informants ranged from 30 to 70 years; 56.19% of the informants were between 50 and 60 years. Twenty-seven (27) of the 105 respondents were illiterate, 59 had first school leaving certificate (FSLC), 12 possessed Senior School Certificate (SSC), 5 obtained Ordinary National Diploma (OND) or National Certificate in Education (NCE) while the remaining 2 held higher national diploma (HND) or a first degree (B.Sc./B.A.). Only one (1) respondent, by marital status, was single. Others were married (99.29%), divorced (2.86%) or widowed (1.90%). A large percentage (68.57%) of the respondents practiced Christianity, 14.29% practiced Islam while 17.14% practiced African traditional religion. Ninety-seven (97) of the informants are native of the study area; eight (8) respondents informed that they migrated to the area and had been residing for 10-15 years in the communities. Clearly, majority of the informants had been residing in the study area for more than 15 years. The respondents were herb sellers (25.71%), herbalist (34.29%), farmers (20%), artisan (5.71%), traders (1.90%), birth attendants (2.86%), and civil servant (9.52%). Table 2 shows the profile of the plants used for medicinal purposes based on the "doctrine of signatures". Sixty (60) plants belonging to 37 families having characteristics that relate to the medicinal uses are documented. The characteristics/signatures mentioned are shape/structure of fruit/pod and leaf, colour of stem bark and root, colour of latex from leaf/leaf extract, seed set, taste of leaf extract, texture of stem bark, and local/vernacular names of the plants. The medicinal applications vary and include anti-malaria, blood tonic/booster, personal protection, favour of the elders, maternal issues, and ease of delivery etc. In majority of traditional cultures or illiterate societies or educationally less-privileged communities, this "law of similitude" serves a symbolic purpose and helps to transfer medicinal information from generation to generation; it also serves as a mnemonic aid for apprentice learning by observation (Bennett, 2007). It is believed, traditionally in Nigeria, that food and drinks which are sweet or sugary are not good for the body as they increase the sugar content of the body, and if not checked could probably result in pile or hemorrhoid. This lends some credence to the use of plants like Azadirachtha indica, Petivera alliaceae, Vernonia amygdalina, and Morinda lucida as anti-malarial plants. These plants are generally called "bitters" and are common trade medicines hawked by herb vendors in Nigeria. Others such as Kigelia africana and Ipomoea batatas formed part of recipes used in the treatment of breast disorders. Majority of the human populations in the world have employed this concept of signatures to prevent or cure diseases, or to bring physic to a particular body organ (Lev, 2002).
The colour of extracts from leaves/stem bark/root/ rhizomes or latex/juices of some plant parts confers the "signature" and suggests their medicinal applications. In this category are: decoction of Sorghum bicolor (blood supplement), and latex of Euphorbia laterifolia (to manage ear ache). This finding is in agreement with Richardson-Boedler (1999) who reported the significance of colour and form of the leaves of Hepatica triloba (liverwort) to its healing powers on human liver. Also, Dafni et al. (1984) noted that the doctrine reflected in the use of the yellow decoction obtained from leaves of Rhamnus alaternus and the yellowish juices from fruits of Ecbalium elaterium for jaundice. Oil from roasted leaf of Bryophyllum pinnatum is used to alleviate ear ache while seeds of Garcinia kola are stimulants for the hepatic duct.
The texture and/or appearance of some plant parts (leaf surface and stem bark indentation) complied with the signature concept. For example, Trema orientalis and Dalbergia lactea are used in the management of measles and skin diseases respectively. The fruit shape of K. africana, the stem latex of Alstonia boonei, and the fruit and stem latex of Carica papaya make the plants important botanical galactogogues; these plants are also used to treat ailments relating to the mammary glands. Kumath (2015) informed that yellow flowers, latex, and dyes are used to treat jaundice while plants that have white latex are used as galactogogues.
Plants such as Cissampelos owariensis (jokoje, sit down quietly) and Uvaria picta (alupayida, sleight-ofhand) feature in magical traditions. These plants are used to work on people's emotions and make them apathetic, and to impress invisibility respectively. The compact arrangement of the seeds of Aframomum melegueta (atare) informs its use by pregnant women to prevent miscarriage. Richardson-Boedler (1999) described the correlation between plant characters and human symptoms. Hocking (1977) reported that the surface sculpture of nutmeg kernel (Myristica fragrans) has a similitude to the superficies of the brain; hence its use as a cerebral or neural medicinal agent.
Animals, minerals, and chemicals have also found a place in the "law of correspondence" (Richarson-Boedler, 1999). Pliny (Gaius Plinius Secundus, AD 23-79) correlated the lungs, liver, and stomach of lower animals with human organs and used these in treating the diseases of these organs in man (Hocking, 1977). Plant chemical investigations have shown that phytochemicals such as monoterpenes and bitter principles (in V. amygdalina, Ocimum gratissimum etc.) correlate with physical properties and healing potentials of the plants (Bennett, 2007). A similar study was conducted in Zimbabwe by Nyazema et al. (1994). Although the authors compared the efficacy of praziquantel and some medicinal plants based on the doctrine, it was established that the plants complied with the signature concept. The findings of the present study are in line with our previous reports (Erinoso and Aworinde, 2012;Aworinde and Erinoso, 2015).
The proponent of the "law of similes", Paracelsus (Theophratus Bombastus von Hohenheim, 1493-1591) and his followers have received heavy criticisms after the concept was introduced into the herbal lexicon, and as such the concept has been regarded as fanciful, farfetched, pre-modern, pre-scientific, primitive, unreliable, and unscientific (Bennett, 2007; see Table 2 for recent assessments and sources). Nonetheless, association with a signature makes it easier to remember a plant and transmit knowledge about its use (Bennett et al., 2002). This association also has physical as well as psychological/spiritual undertones.

CONCLUSION AND APPLICATION OF FINDINGS
This study confirms the knowledge and application of the "doctrine of signatures" in plant uses among the Ikale and Ilaje people of Ondo State. In the "art of signs" or "law of correspondence", plant characters such as colour of extracts/latex, taste of decoctions, shape of plant organs as well as the local name of plants serve as guides in the use of these plants for medical purposes. In other words, like colours, shapes, and characteristics in plants cure those same or corresponding colours, shapes, and other characteristics in the body part or disease in animals and humans. This research finds application in future plant exploration and the development of new drugs to combat