Genus Miliusa: A Review of Phytochemistry and Pharmacology

Background Genus Miliusa (family Annonaceae), widely distributed in mainland Asia and Australia to New Guinea, has been employed in both traditional herbal uses and pharmacological medicines. Original research articles related to this genus are now available, but supportive reviews highlighting phytochemical and pharmacological aspects are now insufficient. Objective This account is an overview of most of the compounds isolated from this genus, along with their pharmacological evaluations. Conclusion A vast amount of data showed that genus Miliusa contained various classes of secondary metabolites. Herein, more than two hundred constituents were isolated, comprising alkaloids, geranylated homogentisic acids, flavonoids, lignans, neolignans, terpenoids, acetogenins, styryls, lactones, phenolics, amides, alcohols, and furfural derivatives. Novel miliusanes and bicyclic lactones have been remarkable characteristics of Miliusa plants. Essential oils from these plants were also detected, with a high amount of β-caryophyllene. Numerous in vitro biological researches on, for example, anticancer, antifungal, antimycobacterial, anti-inflammation, and cardiac activity, especially in terms of cytotoxicity, using either isolated compounds or plant extracts, implied that Miliusa phytochemical components now set out to have a key role in pharmacological development. M. smithiae ethyl acetate extract and its flavonoid ayanin (75) inhibited the growth of MCF-7 cell line comparable with positive control ellipticine. (+)-Miliusol (72) stimulated in vivo anticancer experiment against HCT116 xenograft mouse tumor following the p21-dependent induction of cellular senescence mechanism.


Introduction
People around the world have been extensively using herbal plants and their products for healthcare objectives. As can be seen, the aromatic medicinal plants have been extensively researched as an important resource of commercial drugs because of their wide traditional uses and pharmacological potencies [1]. Natural products are also recognized to be among the richest resources for new drugs and/or drug leaders due to their high structural diversity as they are not available throughout synthetic pathways [2]. Genus Miliusa (family: Annonaceae) comprises about 60 species and is widely native throughout India and Bhutan to Australia and New Guinea, but mostly found in many Asia countries such as Vietnam, Thailand, and China [3].
More than thirty newly rare secondary metabolites belong to derivatives of geranylated homogentisic acid; in particular, the serial novel miliusanes I-XXXI could be seen as characteristic signals to recognize plants from genus Miliusa.
In Southeast Asian traditional medicines, M. balansae species was used for gastropathy and glomerulonephropathy, M. velutina was recommended as tonic and aphrodisiac medicine, or with Thai people, M. thorelii species, also known as "Maa-Dam", was applied to analgesic treatment [7,8].
Secondary metabolites from medicinal plants of genus Miliusa are renowned for traditional uses and pharmaceutical potentials. However, there have not been specific reviews to assess the value of this genus, to the best of our knowledge. The current paper deals with most researches over the past 20 years related to Miliusa species and has given a great insight into the botanical description, the correlated chemical isolated compounds in phytochemical aspect, and their role in pharmacological applications. Databases used to search for literature mostly rely on the Plant List, SCI-Finder, Google
An additional significance in phytochemical works related to plants is that the leaf of M. cuneata species is likely to be a rich source of oxo-protoberberine alkaloids. In 2005, five new alkaloids of type oxo-protoberberine were isolated from the acetone extract of M. cuneata leaf, trivially named miliusacunines A-E (18-22) [7].

Geranylated Homogentisic Acid Derivatives.
Phenolic acids of type homogentisic acids are usually detected in both terrestrial plants and bacterial pathogenic strains [44,45]. Homogentisic acids indicated the significant antioxidant and anti-inflammatory capacities, but the excess accumulation of these can cause "alkapton" symptom in the human body [45,46].
Considerable attention should be paid to the novel class of geranylated homogentisic acid derivatives from plants of genus Miliusa. Among the total forty-one isolated compounds 33-73, secondary metabolites 40-73 were novel and relatively rare compounds in nature while a number of isolates 35-39 were new in literature.
Of isolated compounds 40-72, most of these unique structures might possibly be formed by a rare C-18 skeleton, containing a characteristic -lactone spiro-ring system. Fivemember -lactone ring were geranylated in the structures 40-57, 61-67, and 72, but were found to be opened in the structures 58-60 and 68-71. Two isolated compounds 59-60 also contained a tetrahydrofuran ring. Additionally, the combination of NOE effect observations, Mosher reactions, and X-ray measurements allowed for determining the absolute configuration, in which 1R,5S,1 R-form and 5 -orientation were suitable for the group of compounds 40-72 [14]. 13 C-NMR provided the evidence of chemical shifts C , thereby showing that, at carbons C-1, C-5, and C-1 of compounds containing spiro-ring system, C reached ca. 52.0-56.0 ppm, ca. 63.0-68.0 ppm, and ca. 26 ppm, respectively. Novel (+)-miliusate (40) was one of the interesting constituents of Vietnamese plant M. balansae [31]. After that, it was reported appearing in two other species: M. sinensis leaf, twig and flower, and M. umpangensis leaf [14,19,33,34]. So far, the methanol-water extract (95:5, v/v) of  Vietnamese plant M. balansae leaf and branch has shown to comprise one novel compound, (+)-miliusol (72), and one new natural product, miliusolide (73) [30]. In NOE interactions H-3a to H-5 and H-7a were key evidence to determine these three protons with oriented cis-shape and the absolute configuration was established as 3aS,5S,7aR in compound 73.
Novel geranylated homogentisic acids derived Miliusa plants were more commonly referred to by their trivial name. By using Table 1 and Figure 2, we continue to make comments relating to a serial number of (+)-miliusanes I-XXXI (41-71). Secondary metabolites 41-60 were separated from dichloromethane extract of the other Vietnamese plant M. sinensis leaf, twig, and flower, whereas the remaining members 61-71, once again, derived from M. balansae species [13,14]. As shown in Figure 2, the plausible biogenetic pathway explained why these compounds were classified as geranylated homogentisic acids, in which the first step involved the combination between precursor homogentisic acid and geranyl unit of geranyl diphosphate (geranyl PP). Obviously, the methylation of intermediate product A produced compound 53 while lactone ring-cyclization and dehydrate applied to A would give 72; compound 53 was then joined to epoxide ring-cyclization reaction and dehydrated to form 59 [14].
The most important information to be gained from structural features is that isolated flavonoids derived from Miliusa species were generated as mono-flavonoid derivatives. The phenomenon of methoxylation occurred at carbon C-3 of most isolated flavonols. Normally, flavonols and flavanones were associated with substituents at carbons C-5, C-6, C-7, C-8, C-3', and C-4' by hydroxy and methoxyl groups.

Lignans and Neolignans.
We continuously provide the next phytochemical profiles of the other class of isolated compounds. Starting with the deepest aim to find biologically active molecules from genus Miliusa, four lignans 117-120 and twenty-four neolignans 121-144 have also been isolated (Table 1 and Figure 4). In addition, these phytochemicals from genus Miliusa originated from three parts, leaf, stem, and twig, of two main species, M. fragrans and M. mollis, but occasionally found in M. cuneata species [8][9][10]24].

Acetogenins and Lactones.
A bit of the attractive phytochemical outcome arose from the class of isolated acetogenins. As we know, acetogenins and their analogs are now remarkable characteristics of the family Annonaceae [47]. From Table 1 and Figure 5, isolated acetogenins existed in bark, stem bark, flower, and leaf of M. velutina species and they were new compounds except for goniothalamusin (158). The most striking feature is that these isolated compounds were able to form up to one or two triple bonds in a long aliphatic side chain terminated by -hydroxy (ormethoxyl)--lactone unit, methyl group, or double bond.
Earlier phytochemical report by Jumana and coauthors (2000) showed that acetogenins A-B (145-146) obtained from Bangladeshis M. velutina species reached up to 0.00154% and 0.008% of extract weight, respectively [5]. However, NMR data of long alkyl side chain of these two compounds remain unknown. Paying attention to the result of phytochemical study on n-hexane extract of Thai M. velutina stem bark, based on repeating chromatographic columns on silica gel and sequential LiChrosorb RP-18 column techniques, we found that eight new compounds, alphabetically named cananginones A-I (147-155), have been successfully isolated as colorless viscous liquids [40]. Taking cananginone A (147) as an example, this new C23 linear olefinic acetogenin is accompanied by a variety of significant chemical shifts Miliusolide and its dihydro derivatives 156-157 were also new derivatives of acetogenin detected in M. velutina stem bark [39]. Unfortunately, the trivial name 'miliusolide' was used for both metabolites 73 and 156 [30,39].
In the light of phytochemical research, Wongsa and partners (2017) continuously provided the outcome relative to Thai M. velutina species ( Figure 5) [38]. From n-hexane and ethyl acetate extracts of leaf of this plant, a rare class of eight bicyclic lactones with a C18 carbon backbone, trivially named velutinones A-H (161-168), were isolated. Similar to acetogenins, these compounds were collected with the physical property of colorless viscous liquids. Furthermore, they had shown the same feature in chemical structures, by which geranyl groups are located at carbon C-2a and the relative configuration at carbons C-2a and C-6a was syn-model (2aR,6aR). In general, it is worth concluding that olefinic acetogenins with terminated -lactone and 2-geranylated bicyclic lactones indicated a great crucial role in chemotaxonomic aspect to recognize M. velutina. Lactones in genus Miliusa were also found in M. balansae; the two known compounds curcolide (159) and serralactone (160) were two components of the leaf of this plant, collected from Vietnam [11].
3.6. Styryls. Most of secondary metabolites of interest to chemists pointed out that styryl derivatives were found in genus Miliusa. Styryls presented as the significant constituents of the two species M. balansae and M. velutina [31,32,38,41]. As shown in Table 1 and Figure 6, the three mono-styryls 169-171 and the five bis-styryls 172-176 have been updated. It is worth noting that yangonin (171) was, for the first time, reported from genus Miliusa, while the seven remaining isolates 169 and 172-176 were reported to be new compounds in nature.
Regarding isolated compounds of type bis-styryls, the general chemical structure was designated by cyclobutyl nucleus, while side chains were made up of phenyl rings,pyrone rings, and , -unsaturated ketones.
In order to identify bioactive constituents, phytochemical investigation has been carried out on methanol-water extract   Table 1 and Figure 7, which were newly isolated compounds or isolated for the first time from genus Miliusa [11,25,30,32,37,42].

Amine, Amide, Alcohol Derivatives and Miscellaneous
Types. A phytochemical survey conducted by Yu and partners (2009) pointed out that M. balansae leaf, collected from China, has also been composed of one amine adenine riboside (199), and two amide allantoin (200), and uridine (204) (Figure 8) [26]. Although these compounds are now available in the natural plants, they were isolated as single compounds from genus Miliusa for the first time. Utilizing silica gel (63-200 m) and sephadex LH-20 columns in the chromatographic isolation, three tyramine derivatives, N-trans-caffeoyltyramine (201), N-trans-coumaroyltyramine (202), and N-trans-feruloyltyramine (203), have been purified from acetone of M. cuneata air-dried twig [7]. Since then, acetone extract of M. thorelii stem and root was demonstrated to contain two isolates, 201 and 203 too [8].
Vietnamese M. balansae species might have been considered as a rich resource of diverse compounds. Based on the evidence of phytochemical findings and NMR explanations, six well-known alcohol derivatives, 205-210, were further obtained from the leaf of this plant for the first time [11]. Among them, -D-glucopyranoside (Z)-3-hexenol (205) was a glycosylation of long n-alkyl side chain alcohol, while the five remaining ones 206-210 were categorized as two pairs of erythro and threo isomers of glycerols and one other glucosylated glycerol. They were erythroguaiacylglycerol (206), threo-guaiacylglycerol (207), erythro-1-C-syringylglycerol (209), threo-1-C-syringylglycerol (210), and (L)-guaiacyl glycerol 2 -O--D-glucopyranoside (208), respectively. There were also records of these compounds from genus Miliusa for the first time. As can be seen, the difference of chemical components from Vietnamese and Chinese M. balansae species has been depending on geographic factor more often.
Besides the presence of the rare compounds of type homogentisic acid derivatives, the ethyl acetate extract of airdried M. velutina fruit also consisted of furfural derivatives, in which three small molecules, 5-acetyloxymethylfurfural (211), 5-hydroxymethylfurfural (212), and 5-methoxyfurfural (213), were isolated [32]. Despite the fact that these compounds were formulated with a simple pattern, they were recorded from the plants of genus Miliusa for the first time.  As shown in Figure 9 and Table 1, the common chemical compounds of type phytosterols can be found in several Miliusa plants. For instance, M. balansae stem was reported to contain -sitosterol (216), and its glucoside (217), or stigmasterol (219); this one turned out to be one of the components from both M. sinensis leaf and branch and M. velutina fruit and flower [25,32].
Chromatographic separation of the extracts from M. balansae stem also led to the isolation and determination of two mono-saccharide D-glucose (214) and sucrose (220) whereas M. balansae leaf and branch were accompanied by the existence of fatty acid octacosanoic acid (215) and benzoate sodium (218) [26,32,41].
3.9. Essential Oils. For a long time, there have been researches related to essential oils, which have frequently played an important role and been regarded as a branch of either phytochemistry or pharmacological products findings [1]. Many studies focused on the applications providing multifunction in healthcare problems, alternative medicines, food and drink manufacturers, or household cleaning products. Normally, the distillation method, often by using water steam, is a prompt and efficacious way; in addition, the extractions of solvent or florasols have always been used depending on the raw materials. The systematic GC and GC-MS techniques are usually being used to identify volatile individuals. Miliusa species are also among the largest sources of this specific chemical compound. In the review of all circumstances, following the results of ethno-geographic distribution, species property, part use, extraction method, and GC-MS technical analysis, the results of studying essential oils of Miliusa species were compiled in Table 2.
Essential oils studies on Miliusa plants are quite limited. There have been only three reports to date. Among fortysix members identified from essential oils of fresh leaf of, Quang Binh, Vietnamese M. baillonii species, the main constituent Z-citral reached the highest amount of 41.2% [28]. M. sinensis species, collected from Nghe An, Vietnam, is also likely to be a rich resource of essential oils. From this plant, 67.1% of a total of 95.1% of essential oils were sesquiterpene hydrocarbons [29]. Significantly, -humulene and -caryophyllene could be seen as the main components of oils of these two Vietnamese Miliusa plants (Table 2). In the same manner, the properties of plants, environmental factors, and collection time accounted for the differential components in essential oils of three, Queensland, Australian Miliusa plants, M. brahei, M. horsfieldii, and M. traceyi [27]. As can be seen from Table 2, these three species yielded oils, in which terpenoids predominated. -Humulene,caryophyllene, and bicyclogermacrene achieved more than 10% of oils of M. brahei, while the major sesquiterpene of type caryophyllene derivatives ranged from 12% to 20%, present in M. horsfieldii oils; the highest components in oils of last plant M. traceyi encountered were the two isomers -and -pinene (approximately 19%). Of particular interest, -caryophyllene was found to be one of the main compounds in all the five species (Table 2), which accounted for 10% to 20% of oils of Miliusa species.  Table 3. Earlier report in 2000 by Jumana and partners mentioned the cytotoxicity of constituents from M. velutina species; the LC 90 results of tested compounds may run as acetogenin A (145) (LC 90 7.1 g/mL) > acetogenin B (146) (LC 90 14.1 g/mL) > positive control vincristine (LC 90 15.0 g/mL) > goniothalamusin (158) (LC 90 20.0 g/mL) [5]. Nine new acetogenins cananginones A-I (147-155) were found to possess the weak IC 50 values of 16.6-129.7 M or be inactive in the cytotoxic assay against three cancer cell lines KB, MCF7, and NCI-H187, when compared to those of reference compound doxorubicin (IC 50 0.46-1.05 M) [40].

Pharmacological Activities
Huong and partners (2004b) pointed out four flavonoids, 75-76 and 94-95, from Vietnamese M. balansae plant not just to show their powerful capacities (IC 50 < 5.0 g/mL) in cytotoxic assay against the three cancer cell lines KB, Hep-G2, and RD, but also to emphasize that the introduction and modification of functional groups at carbon C-3, C-6, C-3 , and C-4 were reasonable in the different results between pachypodol (95) and the remaining tested compounds 75-76 and 94 [30].
In a comparison between new dihydrobenzofuran neolignan 3 methoxymiliumollin (134) and its analogs decurrenal (123), miliumollin (140), and miliumollinone (141) in the cytotoxic assay against the three cancer cell lines KB, MC7, and NCI-H187 (Table 3), methoxylation would lead to reducing the IC 50 values but the modification of allyl group did not seem to be the way of positive signal [9]. In another case, with the same test to KB, MC7, and NCI-H187 cell lines, the cyto-  [10]. Now, it is pretty noticeable that uncommon bicyclic lactones velutinindimers A-D and F-H (161-164 and 166-168) gave rise to a range of the IC 50 values from 4.0 M to 24.1 M in inhibiting three cancer cell lines, KB, MCF-7, and NCI-H187, and Vero cell line, while three new styryl derivatives 174-176 failed to do so [38]. As discussed above, leaf of M. cuneata was renowned as a reservoir of the diverse classes of secondary metabolites, but there has been a discrepancy between them in the cytotoxic assay [7]. In detail, either alkaloids, amides, flavonoids, or lignans inactivated towards two cell lines, KB and Vero, only geranylated homogentisic acid (+)-miliusol (72) and took part in suppressing these two cell lines with the IC 50 values of 10.2 ± 0.1 M and 13.5 ± 0.5 M, respectively.
Phytochemical studies on Miliusa plants have reached certain successes with isolating and identifying the presence of geranylated homogentisic acids, but more than ever, these compounds were further set to justify the cytotoxicity.
Isolated compounds 33-37 possessed the cytotoxic activities against the four cell lines KB, MCF-7, NCI-H187, and Vero with IC 50 values in the range of 5.8-40.4 g/mL, and the failure of the two compounds 38-39 (IC 50 > 50.0 g/mL) led to a hypothetical suggestion that the modification of double bond of geranyl unit would not be considered as a good method to promote the positive signal in assay [32].
As part of the ongoing effort to improve the efficacy of miliusane derivatives, recently, nineteen isolated compounds, (+)-miliusate (40) antitumor activities towards NCI-60 panel of human cancer cell lines, but were more active with HCT116 cell line [13]. In a comprehensive analysis, the main component of Miliusa plants, namely, (+)-miliusol (72), was highly recommended to anticancer drugs development. At the end of 21st day of in vivo anticancer treatment, this compound (20.0 mg/kg) induced the decrease in average size of excised HCT116 xenograft mouse tumor up to 72.7%, and the mechanism may be due to p21-dependent induction of cellular senescence rather than apoptosis [13].  [7]. It should be noted that among the four flavones 76, 83, 87, and 95, methylation at 5-OH and methoxylation at carbon C-6 can be responsible for promoting antimalaria, in contrast to the phenomenon dioxane-cyclization between two hydroxyl groups at C-3 and C-4 , whereas hydroxylation and methoxylation at meta-position of caffeoyl unit induced the potential differences among the three amides 201-203.
In addition to antimalarial assay, two known isolated compounds 33-34 and new one miliusanone A (36) inhibited the growth of P. falciparum with the IC 50 values of 3.3-3.9 g/mL but better than those of analogs miliusanone A (37) (IC 50 5.2 g/mL), miliusanal (35), and miliusanones C-D (38-39) (IC 50 > 10 g/mL) [32]. From these data, it was also concluded that among the four geranylated homogentisic acid derivatives 33-34 and 36-37, the number of ester groups in the structure seemed to be the main for the outcome.
Serial new acetogenins cananginones A-I (147-150 and 152-155) failed to inhibit P. falciparum except for cananginone E (151) (IC 50 24.4 M) [40]. Comparing between the structure 151 and the close group of compounds 152 and 154-155, dihydroxylation of double bonds and methylene reduction would not be facilitated.
Three new bulk styryl derivatives, velutinindimers A-C

Antifungal and Antimycobacterial Activities.
In the search for natural products against DNA repair mutant in the yeast strain Saccharomyces cerevisiae, the MeCOEt extract of M. CF. banacea root showed inhibited rad 52. top 1 (IC 12 2000 g/mL), but failed to do so with rad 52 and rad + (IC 12 > 8000 g/mL) [4]. In the meantime, new alkaloid 10-hydroxyliriodenine (7) and positive control camptothecin afforded the respective IC 12 values of 72 g/mL and >20 g/mL in suppressing rad 52. top 1, being better than that of 10-methoxyliriodenine (14) (IC 12 113 g/mL).
The effect of new cananginones H-I (154-155) on fungal C. albicans has been shown to be associated with the IC 50 values of 75.2 M and 37.4 M, respectively, but new acetogenins cananginones A-G (147-153) did not appear active [40]. Herein, the reason is opposite to antimalarial analysis when four structures 151-152 and 154-155 were considerably compared.
The global health problem in developing countries is becoming increasingly involved in growing and expanding of microbacteria. Historical records have accumulated evidence showing that the use of traditional antibiotics, which are derived from synthetic substances, is always accompanied by a long duration of treatment, high cost, and drug resistance [48]. Therefore, calls for new antibiotic drugs from natural sources in the fight against multidrug-resistant bacteria are always strategy.
In a short communication, various components from M. tomentosa species suppressed the growth of several kinds of bacteria and fungi, but the most significant finding is that leaf volatile oil extract reduced the growth of bacterium Bacillus subtilis NCIM 2250 and fungal C. albicans NCIM 3471 with the same MIC value of 0.62 mg/mL, being better than those of leaf aqueous extract (2.5 mg/mL and 5.0 mg/mL, respectively) [49].
Acetogenin A (145) and goniothalamusin (158) are associated with the moderate antibacterial activity with diameters of the inhibitory zone of 9-14 mm against positive Gram bacteria Bacillus cereus, Staphylococcus aureus, and Streptococcus -haemolyticus and 9-11 nm against negative Gram bacteria Salmonella typhi, Shigella flexneri, and Shigella dysenteriae, whereas acetogenin A (146) only influenced B. cereus with diameter zone of 11 mm [5].
The MIC values ranged from 32.0 to 64.0 g/mL, which were the moderate antibacterial result of two geranylated homogentisic acids, 33 and 35, repellent positive Gram bacteria B. cereus DMST 5040, S. aureus DMST 8013, and methicillin resistant S. aureus. Meanwhile, two other geranylated homogentisic acids, 34 and 36, and two styryls, 171 and 175, were only found to be associated with the MIC values of 64.0-128.0 g/mL against B. cereus DMST 5040 [32]. It was, therefore, concluded that geranylated homogentisic acids seemed to be better candidates for this problem rather than styryl derivatives.
At the same time, compound 33 revealed the MIC value of 50 g/mL to treat Mycobacterium tuberculosis H37Ra compared with that of the similar structures 34-39 (MIC > 50 g/mL) [32]. Apparently, substituting groups R 1 and R 2 demonstrated the great role affecting the results.

4.5.
Anti-Inflammatory Activity. Inflammation can be seen as a part of the complex biological response of the body tissues to harmful stimuli, such as irradiation, physical damage, metabolic overload, or infection [20]. Nowadays, modern diseases, for instance, cardiovascular and neurodegenerative disorders, are closely related to inflammation. Suppressing NO production is recognized to be a useful strategy for this problem.
On the screening of anti-inflammatory activity, by using mode of lipopolysaccharides (LPS) (1.0 g/mL)-induced NO production in microglial RAW 264.  [11].

Antioxidant Activity.
Although phytochemical investigation of M. wayanadica species has not yet been performed extensively, its ethanol leaf extract was observed to be equivalent to or better than positive controls in antioxidant assays. For instance, in DPPH assay, the IC 50 value of 465 g/mL arising from M. wayanadica ethanol leaf extract was comparable with those of standard compounds BHT (570 g/mL) and BHA (615 g/mL); with regard to the ferric reducing antioxidant examination, the IC 50 values for these three objects reached 600 g/mL, 835 g/mL, and 870 g/mL, respectively [50].
4.9. Cardiac Activity. Chrysosplenol C (77), a flavonol, isolated from M. balansae, proved to be an essential backbone to induce a positive inotropic effect on rat ventricular myocytes [12]. This compound caused the contractive percentage of ventricular cell and the active percentage of cardiac myosin ATPase up to 53.0 ± 4.07% at 50 M and 28.1 ± 1.20% at 10 M, respectively, compared with those of positive control omecamtiv mecarbil [59.3 ± 2.60% at 400 nM and 80.4 ± 2.89% at 10 M, respectively] [12].

Conclusion
Taken together, Miliusa species have been fully researched in both phytochemical and pharmaceutical aspects, and a general view of the previous results has been outlined in the current paper. This review mostly focused on the knowledge about botanical description, phytochemistry, and biological evaluation. Basic findings might be concluded as below: (i) Miliusa plants are widely distributed in tropical and subtropical regions, particularly Asia mainland.
(ii) Based on morphological analysis and the heavy support of DNA-barcoding techniques, the number of new Miliusa plants discovered increased more often. Up to present, approximately sixty species were identified.
(iii) More than ten Miliusa species were highlighted in studying phytochemical and pharmacological aspects. Among them, Miliusa plants, collected from Vietnam, Thailand, and China, were major objectives for phytochemical investigations.
(iv) A variety of secondary metabolites have been successfully isolated. In the current paper, we draw a list of twenty-two hundred isolated compounds. Chemical constituents derived from Miliusa have fallen into multiple classes of compounds, such as alkaloids, flavonoids, terpenoids, styryls, and lactones, but serial novel derivatives of geranylated homogentisic acid could be seen as biomarkers to recognize Miliusa species.
(v) The geographic factors, environment, and collection time can be responsible for the difference in chemical components of each country. For instance, Thai M. mollis and M. fragrans plants established the high amount of lignans and neolignans whereas some Vietnamese Miliusa plants were characterized by the rich flavonoids, terpenoids, or miliusanes.
Evidence-Based Complementary and Alternative Medicine 27 (vi) Naturally occurring isolated compounds and plant extracts of this genus have been subjected to various pharmacological types, but cytotoxic assay seemed to be the main content of previous researches.
(vii) It was also observed that the biological activation or inactivation of tested compounds closely depended on the key role of functional groups in the chemical structures.
Finally, plant growing proposals, scientific assessments, and extensive phytochemical discoveries on this valuable source ought to be a willingness for drug leads and future pharmaceuticals. Bioactive compounds, in vitro and in vivo pharmaceutical analyses, clinical applications, and unknown mechanism explanations are expected.