Plant tissue extracts prepared from corn, periwinkle, celery, and lettuce contain substance(s) which are inhibitory for spiroplasma growth in culture media. The inhibition titer, measured as the highest dilution of plant extracts which block spiroplasma growth, is inversely proportional to the spiroplasma concentration used for testing. At a concentration of 104 cells/mL, the growth of four spiroplasma isolates investigated (corn stunt spiroplasma, Spiroplasma citri, honey bee spiroplasma, and Bermuda grass (Cynodon dactylon) spiroplasma) was suppressed by the addition of corn and periwinkle extracts up to dilutions of 1/160 and 1/1280, respectively. Spiroplasmas remained viable in extract-supplemented media for at least 5 days and continued to multiply shortly after the plant extract was removed. These results suggest that (1) the inhibitory action of plant extracts is spiroplasmastatic, and (2) inhibitory factors may temporarily bind to cytoplasmic membrane and subsequently suppress the process of cell replication. The anti-mycoplasma activity was greatly reduced when the extract was placed in boiling water for 10 min or at 37 °C for 5 days. No loss of activity was detected when the extract was kept at −20 or 4 °C for 5 days.
Formation of Indophenol Reducing Substances by Heat Treatment of Some Plant Tissue Extracts Part II
