The genus Galanthus (Amaryllidaceae) currently contains 25 plant species naturally occurring in Europe and the Middle East region. These perennial bulbous plants possess well-known medicinal and ornamental qualities. Alkaloid diversity is their most distinctive phytochemical feature. A total of 127 compounds (≈20% of all known Amaryllidaceae alkaloids) grouped in 16 structural types have been previously found in Galanthus extracts. Some structural types like galanthindole, graciline and plicamine were first discovered in Galanthus plants. Nine Galanthus species, however, remain unstudied regarding their alkaloid patterns. Intraspecific variability has only been studied in G. nivalis and G. elwesii. Amaryllidaceae alkaloids are molecules with anticholinesterase, antibacterial, antifungal, antiviral and anticancer properties. Galanthamine, isolated for the first time from Galanthus woronowii Losinsk., stands out as an acetylcholinesterase inhibitor approved for medical use by the FDA for the treatment of symptoms of Alzheimer’s disease. Lycorine, narciclasine and pancratistatin are noteworthy cytotoxic and antitumor alkaloids. Structural types like galanthamine, homolycorine and haemanthamine are fairly well studied in anticancer research, but little to no information is available on galanthindole, graciline and other types. This review aims to present an update on the alkaloid diversity of Galanthus spp. and highlight the need for further research on the antitumor potential of these molecules.

Genus Galanthus (Amaryllidaceae) includes 19 species in Europe and the Middle East. The Flora of Bulgaria recognizes two species: G. nivalis L. and G. elwesii Hook. Galanthus elwesii is characterized by relatively high morphological variability, leading some authors to identify some populations as G. gracilis Celak. However, the occurrence of G. gracilis in the Bulgarian flora is disputed. The hypothesis was that populations previously identified as G. gracilis belong indeed to a separate species. Therefore, the objective of this study was to compare G. nivalis and G. elwesii with plants from populations previously identified as G. gracilis. Morphological, DNA, embryological and anatomical analyzes were conducted to meet the objective. The morphological characteristics and DNA dendrogram revealed that G. gracilis and G. elwesii were situated in the same cluster and had significant morphological similarity, whereas plants from populations identified as G. nivalis were dissimilar in morphology and situated in a separate cluster. The revealed features of the generative sphere showed similarities across the species. Scanning electron microscopy (SEM) analyses of the surface revealed that the anticillinal walls of G. elwesii and G. gracilis were straight, while those of G. nivalis were wavy. This research demonstrated that the plants of G. elwesii and those from populations identified as G. gracilis are morphologically, embryologically and genetically similar, thus refuting the hypothesis. This study did not provide sufficient evidence to support the claim of the existence of G. gracilis in the Bulgarian flora; the populations identified as G. gracilis in Bulgaria may be forms of G. elwesii.

The present study examined the distribution and resource capacity of T. terrestris populations in North Bulgaria. Thirty three populations of four floristic regions—Danube plain, North Black sea coast, Balkan foothill region and North Eastern Bulgaria were confirmed by our investigations. Some populations had areas that exceed 10 ha. The results of resource assessment showed that 29 305 kg dry mass of Herba Tribulus terrestris may be collected every year from these areas.

The discovery of natural sources of biologically active compounds is crucial to medicine, organic farming, plant science, etc. Amaryllidaceae alkaloids are unique compounds of plant origin with a wide variety of biological and pharmacological properties. In the present study, six different chemotypes of Galanthus populations of Bulgarian origin were used for the isolation of alkaloid extracts. The alkaloid extracts were analyzed by GC--MS, and their capability to inhibit acetylcholinesterase, Lolium perenne seed germination and root elongation was assessed. In total, 73 alkaloids of 8 main structural types were detected. Tazettine and lycorine types were predominant in G. nivalis samples, whereas tyramine, lycorine, homolycorine and galanthamine types were most abundant among G. elwesii samples. Sample GE2110, containing 74% galanthamine type alkaloids, achieved the strongest inhibition on acetylcholinesterase (IC50 = 1.32 ± 0.09 μg/mL), but also the weakest inhibition on seed germination (8 ± 5%}) and root elongation (43 ± 17%). Sample GN028A, containing 51% tazettine type alkaloids, was established as the best overall extract, with a strong inhibition on acetylcholinesterase (IC50 = 21.86 ± 1.59 μg/mL), L. perenne seed germination (75 ± 16%) and root elongation (99 ± 1%). Plant species rich in these alkaloids could be the base of a novel biocidal agent against pests and weeds.

Hippeastrum papilio (Ravena) van Sheepen is a bulbous evergreen species and considered a potential new source of galanthamine. This natural compound approved by the FDA is used for the cognitive treatment of Alzheimer’s disease. To optimize the galanthamine yield from this species, it is necessary to study the effects of plant age and fertilization on the alkaloid content, as well as alkaloid and biomass accumulation dynamics in plant organs. H. papilio plants of different ages, which were ex vitro acclimatized (age 0) and previously grown for one (age 1) and two (age 2) vegetation seasons, were cultivated in a flood and drain hydroponic system with different fertilizer solutions for six months. Samples from the roots, bulbs, and leaves were gathered at the end of the vegetation, and the fresh and dry biomasses were measured and then analyzed by GC–MS to establish their alkaloid content. Depending on the age and fertilizer, the galanthamine content varied from 4.5 ± 1.8 to 11.2 ± 2.8 mg/g DW in the roots, from 3.4 ± 0.5 to 5.8 ± 1.3 mg/g DW in the bulbs, and from 3.2 ± 0.3 to 5.7 ± 0.6 mg/g DW in the leaves. The main part (53–61%) of galanthamine was accumulated in the bulbs, while the leaves and roots stored 25–30% and 13–19%, respectively. Higher amounts of N, K, and Ca in the fertilizer did not positively influence the alkaloid yield in plants of ages 1 and 2. Despite the lower biomass accumulation per individual, the plants grown for two seasons (age 1) showed a comparable galanthamine yield (per square meter) at the end of vegetation to those grown for three seasons (age 2) due to their higher density of cultivation. The dynamics of alkaloid and biomass accumulation, studied in plants from age 1 during the vegetation season, showed that the highest galanthamine content in the plant organs is at the beginning of vegetation. Still, the end of vegetation is the best time to harvest the plant biomass for galanthamine extraction. Hydroponic cultivation of H. papilio is an interesting alternative for the production of galanthamine.