**Author details**

have been reported to be found in a number of fruits and vegetables [7, 8]. Apple and berries found to have cardioprotective properties and showed positive impact on blood pressure [9]. Anthocyanins are the flavonoid constituents abundant in cell vacuole responsible for pigmentation in flowers, fruits, and vegetables and produced generally during plant under environmental stress [10, 11]. *In vitro* studies showed antioxidative activities of anthocyanins in cell

Carotenoids are considered as the potential natural antioxidant found in fruits and vegetables. They include xanthophyll and carotenes having scavenging of peroxyl radical [16]. Lycopene is common in tomato and berries, while β-carotenes are orange-colored carotenoids abundant

Plant releases a numerous phytochemicals in order to protect it from environmental stresses such as drought, submergence, chemical pollution, UV exposure, pest and disease infection, and several other unfavorable conditions [18, 19]. Through this process, plant produces secondary metabolites and bioactive compounds having potential antioxidative roles [20]. In general, under natural ecosystem, plant releases numerous chemical compounds to the environment from its body and maintains its normal growth and development. However, plant produces several other chemicals/allelochemicals under environmental stress conditions [21–23]. The released allelochemicals create both heterotoxic and autotoxic conditions for the plant and its neighboring species [24]. Under replanting conditions and recycled hydroponics, plant found to produce a number of allelochemicals that inhibit its own growth and development, and this phenomenon has been reported in beans, taro, strawberry, lettuce, several other leafy vegetables, and ornamentals [25–29]. On the other hand, these allelochemicals may play a significant ecological role in controlling weeds, pests, and

Fruits and vegetables are the great source of phytochemicals that play protective role in many age-related diseases. Phytochemical supplementation can benefit human health through supplying specific antioxidative/bioactive compounds which have preventive role in several diseases. Flavonoids are the most common phytochemicals that provide antimicrobial, antioxidant, anticancer, anti-inflammatory, and wound-healing activities. Plant under stress also produces allelochemicals that can inhibit either its own growth or neighboring plant species. Under stress condition, plant-produced allelochemicals may also play significant ecological

roles through controlling weeds, plant disease, and insect pests.

culture systems such as colon, liver, breast, leukemic cell, and keratinocytes [12–15].

**3. Allelochemicals as phytochemicals in the plant rhizosphere and** 

in yellow-orange and dark-green leafy vegetables [17].

2 Phytochemicals - Source of Antioxidants and Role in Disease Prevention

**its ecological role**

plant diseases [30, 31].

**4. Conclusion**

Md Asaduzzaman1,2\* and Toshiki Asao1

\*Address all correspondence to: asadcbt@bari.gov.bd

1 Department of Agriculture, Faculty of Life and Environmental Science, Shimane University, Matsue, Shimane, Japan

2 Olericulture Division, Horticulture Research Center, Bangladesh Agricultural Research Institute, Gazipur, Bangladesh
