A Case Study of the Exotic Poisonous Plants found in Kottayam District, Kerala, India

Poisonous plants contain many harmful biological components which can be dangerous for living organisms upon contact or due to ingestion. The current study is based on extensive field observations aimed to find out the various exotic poisonous plants in the Meenachil Taluk of Kottayam District, Kerala. A total of 19 exotic plants belonging to 10 families and 18 genera were documented. Among these, Apocynaceae and Euphorbiaceae were dominant in terms of the number of species with 5 species each. Moreover, the authors alsoverified the nativity of these plants. The various plant part(s) such as bark, stem, leaves, fruits, latex, and tuber were found to have different types of poisonous compounds. The severity of the illness caused due to these plants and their respective parts depends on the dose in which the organisms ingest their components or the extent to which they make contact with them. People should be aware about such poisonous plants for avoiding various complications.


Introduction
Plants have developed several means of protection from herbivory. Some have toxins while others have developed physical defences such as thorns. The physiologically active toxins of the plants have the ability to damage livestock and humans, equally [1]. Alkaloids, terpenes, tannins, phenolics and essential oils are examples of the chemical toxins produced by plants [2]. Toxicity is mainly based on the dosage of the poisonous components ingested or the degree of external contact of the plant with the skin. Since the number of toxicity studies is quite small, scientists are always searching for toxic plants in order to kill malignant cells or to defeat diseases. A great number of drugs are based on natural compounds obtained from the poisonous plants. However, the problems experienced in controlling the adverse effects of plant poisoning have not been fully explored yet and need further investigation [3,4].
Toxicological studies of medicinal herbs on animal models have shown that some of these plants, such as daouri and juniper tar that are typically used to treat chronic eczema and other skin diseases, may have nephrotoxicity or hepatotoxicity. It shows that the use of these plants, particularly in children, should be reevaluated [5,6].
The effect of these toxins can be mild, although in severe cases they may cause death. A poisonous plant can be defined as the one producing chemical substances which, when taken in a small or moderate amount, can cause a harmful reation in the bodies of the animals and human beings [7].
Natural poisons are toxic chemical substances produced by various species of fungi, bacteria, protists, plants, and animals. Many of these species produce chemicals which are harmful for the human body. One source of poisoning is through external contact, which causes irritation. The ingestion of poison leads to internal poisoning. Other ways include absorption through skin and inhalation via the respiratory system [8]. The current study is mainly intended to document exotic poisonous plants found in the Meenachil Taluk of Kottayam District, Kerala.

Methodology
An extensive survey supported by field observations during 2014-2015 was carried out in an attempt to find and collect various poisonous plants from the area under study.
The documentation of samples was mainly based on field observations, discussions with the local people and the literature review. The taxonomical identification of the collected samples was carried out with the help of the available floras and literature [9,10]. The nomenclature of each specie was authentecated as per the rules specified in the International Code of Nomenclature (ICN).
Herbarium specimens were produced during the field visits by collecting the plants at different reproductive stages and processing them according to the standard protocol [11]. The voucher specimens were deposited in the Herbaria of the PG Department of Botany, Deva Matha College Kuravilangad, Kottayam for future reference.

Study Area
The area selected for the survey lies in the Meenachil Taluk which is situated in the north-eastern region of the ditrict Kottayam (9.36° N and 76.17° E), Kerala. This is an area of diverse habitats ranging from hills and hilloks to lush paddy fields. It is home to the plantations of multiple crops. Due to its tropical climate, humidity rises upto 90% in the rainy season. Besides, it also receives heavy rainfall, upto 3600 mm/year, during the two monsoon seasons. These include the south-west monsoon season (June-September) and the north-east monsoon season (October-November). From March to May, the area receives rainfall with thunder and lightining from pre-monsoon rains. The highest rainfall other than the monsoon is in December. March, April and May are warmer months, while January and February are comparatively cooler. The average temperature ranges between 38.5°C and 15°C. The mainstream population depends on cash crops such as rubber and black pepper to generate an income. Besides these crops, food crops including paddy and tapioca are also cultivated [12].

Results
The current study documented 19 exotic plants belonging to 10 families and 18 genera. Among the 10 families represented, Apocynaceae and Euphorbiaceae were the dominant ones in terms of the number of species with 5 species each. The other dominant family included Verbenaceae with 2 species, while the rest were represented by a single species only. The nativity of the documented plants revealed that they were introduced from the various parts Department of Life Sciences Volume 2 Issue 4, 2020 of the world including Tropical America (7 species), South America (3 Species), Central America (3 species), Madagascar (2 species), Malaysia (2 species), Brazil (1 species) and the Meditterranean region (1 species). The various plant part(s) such as bark, stem, leaves, fruits, latex, and tuber contain different types of poisonous compounds (Tables 1-3).

Discussion
Toxic plants are the plants when touched or ingested in a sufficient quantity, can be harmful or fatal to human beings and other animals. When used in small amounts and in correct proportions, products from these plants can be utilized as drugs and toxins. The beauty of these plants hides the toxicity within them. The toxicity may differ from plant to plant and it depends on several factors, especially on the different chemicals that characterize it. Moreover, it depends on the part of the plant ingested with respect to its concentration and stage of growth.
Mwine and Damme [13] reviewed the Euphorbiaceae family and its medicinal features.
According to them, Euphorbiaceae is among the large flowering plant families consisting of a wide variety of vegetative forms, some of which are plants of great importance. Its classification and chemistry have of late been the subject of interest possibly because of the wide variety of the chemical composition of its members, many of which are poisonous and at the same time useful.
Anacardiaceae The latex produced from the bark of cashew nuts causes burns and inflammations in the mouth and intestines. Its increased concentration reduces blood pressure. The bark of the nut contains a blakish oil which contains phenolic compounds such as cardol and glucosides such as anacardic acid, cagine, galic acid and cagidine [17].
Annonaceae The seeds and bark of the fruit contain the compound annonin. Similarly, the leaves and roots contain aporphine and coryeline [18] Euphorbiaceae The seed contains the glycoproteins known as ricin and ricinin (more poisonous) which are soluble in water. Ricinin is present in seedcoat, leaf, and stem. The oil extracted from the seed is less poisonous. The seed contains glycerides and ricinolic acid. The consumption of seed causes a burning sensation in the throat and the mouth at first and later on the person experiences fatigue, thirst, dizziness, and an increasing heartbeat. It eventually leads to unconsciousness. The oil cake contains more ricin and cannot be used for animal feed. Death occurs suddenly if the oil is injected directly into the blood. The powder of the seeds also causes allergic reactions [33]. 19. Thevetia nerifolia L.
Apocyanaceae The main poisonous part is the fruit. Its chewing causes the drying of the tongue and throat and leads to muscle fatigue as well as the dialation of the iris. The heart beat varies and death occurs due to reduction in the blood flow. The poisonous substances (glucosides) present in the seeds are thevetin and theveresin (which is similar to digitalin) and some crystal particles such as phytosterolin, ahoein, and cocilphin which are cardiotoxic [34].

Conclusion
The [4] Gonzalo JD. Toxicosis by plant alkaloids in humans and animals in