Figure 4.

OPLS-DA plots of Rosmarinus officinalis fractions (first stage RO-5 fraction and its subfractions, RO-5–1 through RO-5–6) in negative (NI) MS mode. The separation pattern of the data points is supervised by the percent inhibition values against MRSA. 5A. OPLS-DA scores plot of the fractions. Each fraction is plotted as an individual data point and color-coded. RO-5–4 having the highest inhibition against MRSA is visualized in the quadrant I, while RO-5–6 with no inhibition against MRSA is in the quadrant II. Other fractions with moderate bioactivities cluster closely to one another near the center of the plot. 5B. OPLS-DA loadings plot of the fractions. The detected features, which exist in the same quadrant as RO-5–4, are clustered in the quadrant I and their presence is highly correlated to the bioactivity of the fraction. 5C. OPLS-DA loadings plot, zoomed in on the features correlating to the bioactivity. The features are color-coded based on the compounds. Similar to thepositive mode, micromeric acid (1), oleanolic acid (2) or ursolic acid (3), and their adducts were identified to be positively correlating to the bioactivity of RO-5–4. The precursor ion [M−H]⁻ of micromeric acid (1) was identified as the most positively correlated ion to the bioactivity of RO-5–4. Additional tentative annotations of the features can be seen in Table 1.