Antibacterial activity of plumbagin derivative-rich <i>Plumbago indica</i> root extracts and chemical stability

<div><p>The extraction studies and a one-step purification of the crude extract of <i>Plumbago indica</i> using silica-gel vacuum chromatography provided a plumbagin derivative-rich <i>P. indica</i> root extract (PPE). The PPE was standardised to contain total plumbagin derivatives not less than 13% w/w. Antibacterial activities of the standardised PPE and three naphthoquinones, plumbagin, elliptinone and 3,3′-biplumbagin, against <i>Propionibacterium acnes</i>, <i>Staphylococcus aureus</i> and <i>Staphylococcus epidermidis</i> were evaluated by using the microdilution assay. The bactericidal activities of the PPE against these bacteria were much stronger than those of elliptinone and 3,3′-biplumbagin and almost equal to those of plumbagin. Stability of the PPE was determined under various conditions through a period of four months. The PPE was stable over a period of four months when stored as a dried powder but only in a well-closed container protected from light under 4 ± 2°C.</p>