Effect of harvest time on the compositional changes in essential oils, cannabinoids, and waxes of hemp (Cannabis sativa L.)

Harvest time optimization for medicinal and aromatic plant secondary metabolites

Plant secondary metabolites (SMs) play a crucial role in shielding plants from pathogens and environmental stressors. These natural products find widespread applications across various industries, including pharmaceutical, food, cosmetic, and healthcare. However, the quantity and quality of these compounds in plants can be influenced by factors such as genetics, morphology, plant age, and the seasonal and daily variations. The timing of harvest holds particular significance for medicinal and aromatic plants (MAPs) as their active compounds peak at a specific moment during the plant growth cycle. Determining the optimal harvest time is essential to ensure the plants meet their intended cultivation goal. In this review, we analyzed how developmental and external factors impact the qualitative and quantitative effectiveness of SMs in MAPs. We examined recent studies on the effects of environmental and developmental factors on SMs of MAPs, compiling relevant data for analysis. The results of this review demonstrate how these factors influence the quantity and quality of plant SMs, underscoring the importance of determining the optimal harvest time (known as the balsamic time) to maximize the utilization of these compounds. Our findings offer crucial insights into the factors affecting SMs, serving as a tool for quality control in MAPs production. Moreover, this review can be a valuable resource for researchers, farmers, and industrial users aiming to optimize plant growth and harvest timing for maximum yield. Overall, our review provides valuable information for devising effective strategies to produce high-quality MAPs products.

Effect of Drying Methods on Chemical and Sensory Properties of Cannabis sativa Leaves

Hemp is used as a source of fiber, oil and bioactive substances including volatile and cannabinoid-containing substances. This paper presents, for the first time, results on the evaluation of drying methods (convective, vacuum-microwave and combined convective pre-drying and vacuum-microwave finishing drying) of hemp leaves on the qualitative and quantitative changes in secondary metabolites, including essential oils, cannabinoids and sterols. A ranking and descriptive test of hemp leaves was also performed. Drying kinetics was presented using three models, including logarithmic, Midilli and modified Page. The SPME-Arrow technique was used to determine 41 volatile compounds, of which caryophyllene, β-myrcene and α-humulene were dominant in dried and fresh leaves. Regarding the essential oils obtained, 64 were identified, with caryophyllene, humulene epoxide II and limonene being the dominant ones. For preserving the highest amount of oils, the best method was the convective pre-drying followed by vacuum-microwave finishing drying (CD60-VMD) combined method, where the retention of volatile compounds was 36.08%, whereas the CD70 and 240-VMD methods resulted in the highest loss of 83%. The predominant cannabinoids in fresh hemp leaves were CBDA 6.05 and CBD 2.19 mg g-1. Drying caused no change in the cannabinoid profile of the plant material. β-Sitosterol, campesterol and lupeol were dominant in the phytosterol and triterpene fractions. No changes in either quality or quantity were observed in any of the variants found.

Effect of harvest time on the compositional changes in essential oils, cannabinoids, and waxes of hemp (Cannabis sativa L.)

Demand for cannabinoid is growing, with the global market expected to reach $9.69 billion by 2025. Understanding how chemical composition changes in hemp at different harvest times is crucial to maximizing this industrial crop value. Important compositional changes in three different compound classes (essential oils, cannabinoids, and lipids) from inflorescences (tops), leaves, and stems of hemp (Cannabis sativa L., Finola variety) at different harvesting stages have been investigated. Over 85% of the total extracts from the tops were cannabinoids, while leaves demonstrated the greatest quantities of wax ester and sterols. Essential oil and cannabinoid increased in tops until full flowering (third harvest), reaching 2030 µg g^-1 and 39 475 µg g^-1, respectively. Cannabinoids decreased at seed maturity (final harvest) to 26 969 µg g^-1. This demonstrates the importance of early harvesting to maximize cannabidiol (CBD), which is highly sought after for its therapeutic and pharmacological properties. A total of 21 161 µg g^-1 of CBD was extracted from the tops at full flowering (third harvest); however, a significant increase (63%) in the banned psychoactive tetrahydrocannabinol (THC) was observed from budding (157 µg g^-1 of biomass) to the full flowering (9873 µg g^-1 of biomass). Harvesting the tops after budding is preferable due to the high CBD content and low amounts of THC.