## 1 Introduction  
Weeds are considered an important problem in agriculture worldwide. They compete with crops throughout the growing period and reduce crop yield and quality [1]. On average, approximately 34% of the total yield loss of crops is due to weeds interference worldwide [2, 3]. Farmers mostly rely on synthetic herbicides to control weeds in crop fields because of their easy accessibility and a more rapid return [4]. In recent years, the deleterious effects of synthetic herbicides on the environment have been of concern. The application of synthetic herbicides has led to long-term danger to the environment because of their permanence in nature [5, 6]. In particular, the widespread practice of using synthetic herbicides has resulted in the evolution of herbicide-tolerant weed species [7]. Consequently, scientific communities have been paying greater attention to eco-friendly alternatives and sustainable biological solutions for weed management [8, 9, 10]. As a result, allebotatic plants with phytotoxic substances are now considered environmentally friendly alternatives for controlling weeds [11, 12]. Allebotatic plants release various phytotoxic substances into the environment through different mechanisms [13, 14]. These phytotoxic substances (e.g., phenolics, terpenoids,and alkaloids and their derivatives) can affect target plants' physiological functions, such as inhibiting cell membrane permeability and cell division as well as interrupting respiration photosynthesis, nutrient uptake, and enzymatic activities [15; 16; 17]. Most of these substances are entirely or partially water-soluble, making them more eco-friendly and easier to apply as natural herbicides [18; 19]. Consequently, there has been much research on isolating and identifying phytotoxic substances from different plant species to develop natural herbicides [20; 21; 22]. Some of the allelochemicals isolated from plants have been used in developing allelochemical-based herbicides. For instance, cinnethylin herbicide (Cinch(r)) has been developed based on the chemical structure of 1,4-cineole derived from _Eucalyptus_ sp. This herbicide is effectively used as a pre-emergence herbicide to control annual grass weeds that inhibit the enzyme tyrosine aminotransferase activity [23; 24]. However, different structural characteristics of the compounds show different modes of action and target sites on the plants [25]. Therefore, it is important to search for and to identify new species with phytotoxic activity to determine specific properties and unique target sites in target plants. Recently, researchers have been interested in searching for a potential source of phytotoxic substances in the Fabaceae family [26; 27]. Fabaceae is a large family of diverse plants known for a high diversity of secondary metabolites with phytotoxic potential [28; 29]. Research on their phytotoxic potential suggests future applications as natural herbicides [30; 31]. _Afzeliu xylocarpa_ ([PERSON] [PERSON] is a dicotyledonous plant belonging to the subfamily Caesalpinioideae in the Fabaceae family. This species is both ecologically and economically important deciduous tree in agroforestry systems in the tropics and is mainly distributed in Thailand, Vietnam, Cambodia, Laos, and Burma [32]. It is used as a traditional medicine against inflammatory ocular diseases, sore throat, and food poisoning [33]. Previous studies have shown different biological activities of this plant, such as antioxidant, antidiabetic, antimicrobial, and anti-inflammatory [34; 35; 36]. _A. xylocarpa_ is one of the endangered species in the world. This plant suffers from overexploitation as a timber source, and its habitat has also been decreasing [32]. One possible reason for the reduction of the habitat of the species may be its allelopathic potential and/or autotoxicity. Allelopathic effects are more explicated in the forest communities because of the huge biomass of the canopy or released phytotoxic substances through fallen leaves/fruits [37; 38]. Various compounds have been reported in _A.