How storage affects the quality of a Ziziphora tenuior's essential oils

Jim Crocker
21st November, 2025

How storage affects the quality of a Ziziphora tenuior's essential oils

Ziziphora tenuior

Photo adapted from: Samarqand davlat unversiteti / CC BY (Source)

Key Findings

  • This Iranian study investigated how storage temperature affects the chemical makeup of Ziziphora tenuior essential oil, a plant with medicinal properties
  • Storing the oil at room temperature significantly degraded key antimicrobial compounds like pulegone and cis-carvone over three months
  • Refrigeration and especially freezing preserved the essential oil’s chemical composition, maintaining the concentration of beneficial compounds
The increasing resistance of bacteria to existing antibiotics is a major global health threat[2]. This situation, sometimes referred to as the ‘post-antibiotic era’, necessitates the exploration of alternative antimicrobial sources, with medicinal plants being a promising avenue. Many plants produce compounds with antibacterial properties, and essential oils – concentrated extracts from plants – are receiving increased attention. However, the effectiveness of these oils can be affected by how they are stored, a factor that hasn’t always been thoroughly investigated. Researchers at Shiraz University recently conducted a study[1] focusing on Ziziphora tenuior, a medicinal plant known for its antimicrobial and antioxidant properties, but currently classified as endangered. The study investigated how different storage temperatures and durations impact the chemical composition of the plant’s essential oil. This is important because the oil’s effectiveness relies on the presence of specific chemical compounds, and these compounds can degrade over time, particularly if not stored correctly. The essential oil was extracted from the air-dried parts of the Ziziphora tenuior plant using a process called hydrodistillation – a method involving steam to separate the oil from the plant material. The extracted oil was then divided into three groups and stored for three months at different temperatures: 25°C (room temperature), 4°C (refrigeration), and -20°C (freezing). The chemical composition of the oils was analyzed using gas chromatography, a technique that separates and identifies the different compounds present in a mixture. The data was then analyzed using statistical methods – Principal Component Analysis (PCA) and Selection Criteria (SC) – to identify patterns and significant changes. The results showed a clear impact of storage temperature on the oil’s chemical composition. At room temperature, there was a significant degradation of compounds with low boiling points. Specifically, the concentration of pulegone decreased from 42.84% to 7.86%, and cis-carvone dropped from 10.1% to 0.99% over the three-month period. These compounds are believed to contribute significantly to the oil’s antimicrobial activity. In contrast, the oil samples stored at freezing temperatures maintained a much more stable chemical profile, with minimal degradation of these key compounds. This study builds on previous research highlighting the potential of Lamiaceae family plants – the family Ziziphora tenuior belongs to – as sources of biologically active compounds[3]. Earlier work identified several compounds within this family, including phenolic compounds, alkaloids, and terpenoids, as having antibacterial potential, often by disrupting bacterial cell membranes or interfering with their metabolic processes[2]. The findings of are also consistent with the idea that essential oils can offer an alternative to synthetic antibiotics, particularly as antibiotic resistance continues to grow[2]. The degradation observed at room temperature suggests that the volatility of certain compounds within the essential oil leads to their loss over time. This is why cold storage is crucial. The study’s findings emphasize the importance of proper postharvest handling and storage practices for essential oils, particularly those derived from endangered medicinal plants like Ziziphora tenuior. Maintaining the chemical integrity of the oil is vital to preserving its biological activity and ensuring its sustainable use in pharmaceutical, food, and health-related applications. Furthermore, the research expands on previous investigations into extraction methods for medicinal plants like Mentha longifolia[4], demonstrating that while extraction is the first crucial step, preserving the extracted compounds is equally important. The study at Shiraz University provides valuable data for establishing standardized practices to maintain the quality of essential oils, contributing to their effective and sustainable utilization.

HerbsBiochemPlant Science

References

Main Study

1) Preservation of essential oil quality in endangered Ziziphora tenuior L. under different storage conditions

Published 18th November, 2025

https://doi.org/10.1038/s41598-025-24422-9

Related Studies

2) Back to Nature: Medicinal Plants as Promising Sources for Antibacterial Drugs in the Post-Antibiotic Era.

https://doi.org/10.3390/plants12173077

3) In vitro biological potential of the essential oil of some aromatic species used in Iranian traditional medicine.

https://doi.org/10.1007/s10787-022-00934-y

4) Comparison of quantity, quality and antibacterial activity of essential oil Mentha longifolia (L.) L. under different traditional and modern extraction methods.

https://doi.org/10.1371/journal.pone.0301558


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