Composition and Antimicrobial Activity of Different Plant Parts of Parthenium hysterophorus L.

This study was aimed to determine the lignocellulosic biomass in different parts of Parthenium hysterophorus and evaluate its antimicrobial activity against selected microbial plant pathogens. Compositional analyses were conducted on live whole plants and their leaves, stems, flowers, and roots. The lignocellulosic biomass components were estimated gravimetrically as a percentage of dry weight, using the standard equation, while reducing sugar was quantified using a glucose standard curve. Significant differences (p < 0.05) in cellulose content were observed among different plant parts, with the highest dry weight percentage in the whole mature plant (48±0.33), followed by the stem (45±0.21), whole young plant (41±0.10), root (21±0.00), leaf (28±0.01), and inflorescence (21±0.14). Additionally, reducing sugar content in mg/mL was significantly higher in the stem (1.94±0.01) and root (1.17±0.00), followed by the mature whole plant (0.95±0.20), leaf-stem mixture (0.93±0.11), inflorescence (0.67±0.02), young whole plant (0.23±0.19), and leaf (0.17±0.01). The stem and root extracts from mature plants inhibited soil-borne plant pathogenic bacteria Pseudomonas sp. and Ralstonia sp. respectively. The leaf and inflorescence extracts of P. hysterophorus showed inhibitory effects only against Pseudomonas sp., not Ralstonia sp. Furthermore, the mature Parthenium plant extract inhibited all tested soil-borne fungi, with significantly higher inhibition percentages observed for Scelerotium sp. (81.93%) and Colletotrichum sp. (45.45%) compared to Fusarium sp. and Pythium sp. Significantly higher cellulose and lignin contents in the whole mature P. hysterophorus plant, along with its antimicrobial activity against major soil-borne plant pathogenic microbes was prominent than the individual plant parts and the young immature plant.