Teak (Tectona grandis L.f.) is one of the most valuable timber species, and is cultivated in agroforestry systems in many countries across the tropical and subtropical regions of the world.
Teak (Tectona grandis L.f.), belonging to the family of Lamiaceae, is a large deciduous tree up to 40 m in height. The leaves are ovate (40 cm long, 20 cm wide) and hairy on the lower surface. It has small, fragrant white flowers attached in panicles at the end of its branches. Teak is one of the most valuable timber species because of its beautiful appearance and durable property [1][2]. Although native to South and Southeast Asia, the significant economic potential of teak wood led the species to be introduced into the agroforestry systems of many countries across tropical Asia, Africa and Central and South America [3][4][5][6][7].
Home gardens in tropical and subtropical countries surround residences of local inhabitants, and create small forest-like structures. They are considered to be the traditional agroforestry systems characterized by complexity of the structure and multiple functions. Home gardens consist of various kinds of tree species, with crops, livestock, poultry and fishes—those species have been selected by local inhabitants for their preference, productivity and sociocultural aspects. Home gardens provide various food and goods, including commodities such as animal products, fruits, vegetables, folk medicine, ornamentals, fodder, timber and fuel [8][9][10][11][12][13]. Teak is one of the most essential trees in home gardens in South Asia, because it is a very precious wood species and important in folk remedies [8][14][15]. Hot water extracts of teak barks are applied for the treatment of bronchitis, biliousness, hyperacidity, diabetes, dysentery, and leprosy. Water extracts of teak leaves are used in pruritus, stomatitis, ulcers and wounds. Hot water extracts of teak roots are applied for anuria treatments. Oil extracts of the flowers are useful for scabies and hair growth. It has also been used as an important plant in Ayurvedic treatments [2][16].
Evidence of the pharmacological properties of teak plants has been accumulated over the past decades. Ethanol extracts of teak leaves have shown significant wound healing activity [17]. Ethanol extracts of teak roots have hyperglycemic activity [18]. Ethanol extracts of teak barks show anti-inflammatory and analgesic potentials [19]. Petroleum ether extracts of teak seeds have hair growth activity [20]. Many compounds with pharmacological activities were also isolated from various parts of teak plants [2][16][21].
Some plants have shown excellent weed control abilities as soil additives and/or in intercropping, due to their characteristics of allelopathy [22][23]. Plants produce hundreds of secondary metabolites. Some of those compounds are released into the surrounding environments through root exudation, volatilization, leaching and decomposition of the plants. Those compounds with allelopathic activity are able to inhibit the growth and germination of neighboring plant species [24][25][26]. Therefore, allelopathy of plants is potentially useful for weed management options in several agriculture settings, including agroforestry systems, for the reduction of commercial herbicide dependency [27][28]. Many phytotoxic substances with allelopathic activity in teak have already been isolated and characterized. However, there has been no review article about the phytotoxic substances involved in teak allelopathy.
Source | Inhibition | Target Plant Species | Reference |
---|---|---|---|
Leachate from leaves | Germination, plant growth | Vigna unguiculata, Momordica charantia, Solanum melongena | [37] |
Cicer arietinum | [38] | ||
Leaf mulch | Rhizome growth | Turmeric | [15] |
Leaf powder | Weed emergence | Cyndon dactylon, Echinochloa colona, Cyperus rotundus, Cyperus difformis, Amaranthus viridis, Chenopodium album, Melilotus alba | [39] |
Extracts | |||
Soil under teak trees | Germination, plant growth | Tomato | [40][41] |
Fallen leaf | Plant growth, protein content | Vigna mungo, Vigna radiata | [42] |
Germination, | Echinochloa colona, Cyperus difformis | [43] | |
Weed emergence | Cyndon dactylon, Echinochloa colona, Cyperus rotundus, Cyperus difformis, Amaranthus viridis, Chenopodium album, Melilotus alba | [39] | |
Fresh leaf | Germination, plant growth | Vigna mungo | [44] |
Germination, plant growth | Plumbago zeylanica | [45] | |
Rice, maize, Vigna radiate, Vigna umbellate, Arachis hypogeae | [46] | ||
Germination | Luffa cylindrical, Abelmoschus esculentus, Brassica juncea | [47] | |
Plant growth, contents of chlorophyll and carotenoid | Chilli, Vigna radiata | [48] | |
Plant growth, contents of chlorophyll and carotenoid | Pennisetum glaucum, Eleusine coracana | [49] | |
Plant growth | Amaranthus spinosus | [50] | |
Root | Germination, seedling growth | Hibiscus esculentus | [51] |
Leaf, root, bark | Plant growth | Maize | [52] |
Phytotoxic substances with allelopathic activity identified in teak are discussed in this section. All phytotoxic substances listed in Table 2 and Figure 1 were isolated from fresh teak leaves with water. Naphthotectone (3) inhibited the germination and seedling growth of wheat (Triticum aestivum L.), onion (Allium cepa L.), tomato (Lycopersicon esculentum L.), and lettuce (Lactuca sativa L.) [53]. Rhinocerotinoic acid (8) suppressed the germination and seedling growth of wheat and lettuce [54]. 2-Oxokovalenic acid (9) and 19-hydroxyferruginol (11) inhibited the germination and seedling growth of wheat, onion, lettuce; 3β-hydroxy-7,8-dihydro-β-ionol (15) inhibited the seedling growth of wheat, onion and tomato; and 3β-hydroxy-7,8-dihydro-β-ionone (16) inhibited the seedling growth of wheat, onion, tomato and lettuce [55]. Other compounds listed in Table 2 inhibited the seedling growth of wheat [54][55][56]. Although those compounds were isolated and identified from teak leaves for potential use as a source of natural herbicide model and/or bioactive compounds, the allelopathic effects of those compounds were determined only by crop plants. It may be necessary to determine the activity of those compounds on weed species.
Phytochemical Class | Compound | Terget Plant Species | Inhibition | Reference |
---|---|---|---|---|
Phenolic | 1: Acetovanillone | Wheat | Plant growth | [56] |
Benzofuran | 2: Dehydrololiolide | Wheat | Plant growth | [55] |
Anthra quinone | 3: Naphthotectone | Wheat, onion, tomato, lettuce | Plant growth, germination | [53] |
Monoterpene | 4: (6RS)-(E)-2,6-Dimethyl-2,7-octadiene-1,6-diol | Wheat | Plant growth | |
Sesquterprne | 5: lβ-6α-Dihydroxy-4(15)-eudesmene | Wheat | Plant growth | [54] |
6: (1S,3aR,4R,7aS)-1-(2-hydroxypropan-2-yl)-3a-methyl-7-methyleneoctahydro-1H-inden-4-ol | Wheat | Plant growth | [54] | |
Diterpene | 7: Phytol | Wheat | Plant growth | [54] |
8: Rhinocerotinoic acid | Wheat, lettuce | Plant growth, germination | [54] | |
9: 2-Oxokovalenic acid | Wheat, onion, lettuce | Plant growth, germination | [54] | |
10: Lab-13-en-8β-ol-15-oic acid | Wheat, onion, lettuce | Plant growth | [54] | |
11: 19-Hydroxyferruginol | Wheat, onion, lettuce | Plant growth, germination | [54] | |
12: Solidagonal acid | Wheat | Plant growth | [54] | |
Apocarotenoid | 13: Tectoionol A | Wheat | Plant growth | [55] |
14: Tectoionol B | Wheat | Plant growth | [55] | |
15: 3β-Hydroxy-7,8-dihydro-β-ionol | Wheat, onion, tomato | Plant growth | [55] | |
16: 3β-Hydroxy-7,8-dihydro-β-ionone | Wheat, onion, tomato, lettuce | Plant growth | [55] | |
Phenylpropanoid | 17: Syringaresinol | Wheat | Plant growth | [56] |
18: Medioresinol | Wheat | Plant growth | [56] | |
19: Lariciresinol | Wheat | Plant growth | [56] | |
20: Balaphonin | Wheat | Plant growth | [56] | |
21: Tectonoelin A | Wheat | Plant growth | [56] | |
22: Tectonoelin B | Wheat | Plant growth | [56] |
Several phenolics were also identified in teak barks and leaves [39][50][57]. Phenolic compounds have been found in a wide range of plants and soils, and often mentioned as putative allelopathic substances [58][59]. The importance and contribution of those phenolics found in teak are not clear because no information regarding the phytotoxic activity of those compounds for teak allelopathy is available in the literature. However, gallic and ellagic acids were identified in teak leaf extracts [60], and the allelopathic activity of those compounds isolated from other plant sources were reported [61][62]. Therefore, some phenolics in teak plants may contribute to the allelopathy of teak. Phenolic compounds inhibit some enzyme activities and physiological processes, such as plant hormone functions, water balance and mineral uptake, as well as stomatal functions, respiration, and photosynthesis [58][63].
A number of secondary metabolites in many classes have been isolated and identified from various parts of teak plants, such as barks, flowers, fruits, leaves and roots. Those compounds were quinones, terpenes, apocarotenoids, phenolics, flavonoids, saponins, lignans and norlignans [16][64]. Teak wood shows resistance to termite and fungal damages, and napthoquinones and anthraquinones contribute a resistance property [65][66][67][68]. Some other compounds were also related to the pharmacological activities of teak [2][16][21][35][57]. Although those compounds have been associated with the pharmacological effects and property of its wood characteristics, some of those compounds may possess phytotoxic activity.
This entry is adapted from the peer-reviewed paper 10.3390/app11083314