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Abstract
We investigated the effect of freezing on the chemical composition and biological activity of bulbs of Urginea sanguinea Schinz, a known ethnoveterinary medicinal plant. Freshly harvested bulbs were extracted as either fresh material or after oven drying. Frozen bulbs were extracted after overnight thawing at room temperature or after thawing and oven drying. The leaves were extracted dried at room temperature. Plant material was finally ground and extracted with acetone. The yield from frozen material exceeded that from nonfrozen material by more than 10%. The chemical composition of frozen bulbs, as analyzed by thin-layer chromatography (TLC), differed significantly between fresh and dried material and marginally between fresh and thawed material. Because U. sanguinea is used for diseases that could be infection-related, we examined the antibacterial activity of the extracts. The minimal inhibitory concentration against Staphylococcus aureus was 1.25 mg/ml for fresh dried and thawed dried. Other fractions had no substantial antibacterial activity. No extract had significant free-radical scavenging (antioxidant) activity. The mechanism of action in ethnoveterinary use is probably not via antibacterial or antioxidant activity or immune stimulation. Although the dried bulbs were more chemically complex, the extractable mass had decreased from fresh to dried material by at least 13%, possibly because of desiccation. Bulbous material is difficult to extract, and freezing before extraction may be a viable option for use in the herbal industry.